J. JONES, Justice.

Lesia Knowlton appeals the Industrial Commission's determination that she is not entitled to workers' compensation benefits because she failed to demonstrate that her medical symptoms were causally related to an accident that occurred during the course of her employment. We affirm.

I.

Factual and Procedural Background

During all times relevant to this appeal, Lesia Knowlton was employed as a unit secretary at Wood River Medical Center. On September 12, 2000, Knowlton was working at her assigned station when a toilet or bathroom floor drain in a patient's room became clogged. The patient's room was located near the area where Knowlton was working. One of the maintenance workers at the hospital used a chemical to remedy the problem. The chemical produced a foul odor, which Knowlton described as an "orange citrusy" smell. In an effort to ventilate1 the patient's room, the hospital staff placed a fan in the doorway of the room, which blew air past Knowlton's station until her shift ended at approximately 4:00 p.m.2 After several people complained about the odor, the director of nurses and the infection control nurse decided to move the patient from the room where the chemical was used to a different room in the hospital. According to Knowlton, the odor got stronger as the day went on, and she began smelling an odor resembling "rotten eggs" coming from the kitchen. Kitchen personnel informed her that the smell was coming from the drains. Knowlton developed a headache as a result of breathing the odor.

After returning home after her shift ended, Knowlton developed a cough and body aches. The following day, Knowlton had to leave work around lunchtime because her symptoms had worsened. Knowlton was only able to work a partial shift on September 14. On September 15, three days after the incident, Knowlton sought medical treatment from Laria Thomas, a nurse practitioner. During this visit, Knowlton reported that she was experiencing a cough, a sore throat, and burning when she would breathe. Knowlton was prescribed antibiotics, cough syrup, and an inhaler. A chest x-ray taken on a follow-up visit with Thomas was normal.

Knowlton returned to work on September 18, and was told that the chemical used on the day of the incident contained sulfuric acid.3 The following day, Knowlton filled out and signed a Form 1 Report of Injury or Illness.

Knowlton visited Dr. Thomas Pryor on September 25. Dr. Pryor's notes from the visit indicate that Knowlton had a cough and bronchitis-like sounds in her lungs. During a follow-up visit on September 28, Knowlton complained of a sore throat and a sore chest from coughing. Dr. Pryor also noted that her sinuses were inflamed, and provided her with a release from work. By October 4, Dr. Pryor noted that the sinus inflammation had "improved profoundly." On the same day, nurse practitioner Thomas also provided Knowlton with a release from work retroactive to the day of the incident. The next day, Knowlton phoned Thomas and reported that she had another negative reaction after being exposed to other cleaners at work.

On October 13, on the advice of Dr. Pryor, Knowlton visited Dr. Ronald Fullmer, a pulmonologist. During this visit, Knowlton complained of shortness of breath and hoarseness. Knowlton also complained that her symptoms increased when exposed to animals, cold air, smoke, and perfume. Dr. Fullmer recognized some vocal distortion, but mentioned that it became more normal when she was not speaking about her initial exposure to the chemical. Dr. Fullmer's examination indicated that Knowlton's head, eyes, ears, nose, and throat were normal. A medical history taken during that visit indicated that Knowlton had been smoking cigarettes for "less than one year." According to Knowlton, she smoked prior to the chemical exposure but quit after the incident.

On October 25, nurse practitioner Thomas prescribed Wellbutrin at Knowlton's request to help her quit smoking. On December 11, Knowlton reported to nurse practitioner Thomas that she had experienced a negative reaction to food on two occasions during which her eyes became itchy and her throat and chest became red. Thomas' notes indicate that Knowlton wondered if she was reacting to some sulfa-containing component in the food. On December 20, Knowlton visited Dr. Fullmer complaining that her symptoms had increased after being exposed to odors from the new carpet and furnishings at her place of employment. Knowlton also mentioned having negative reaction to foods.

On the advice of Dr. Fullmer, Knowlton went to see Dr. Richard Henry, an allergist. While visiting Dr. Henry, Knowlton complained of episodic hoarseness, chest tightness, shortness of breath, and nasal congestion following exposure to strong odors, aerosol sprays, perfumes, and scented soaps. She also mentioned that any products containing sulfur especially aggravated her symptoms. Dr. Henry recommended that Knowlton undergo allergy skin testing.

In January of 2001, Knowlton began to see another pulmonologist, Dr. Holly Carveth. Dr. Carveth determined that Knowlton was suffering from reactive airway disease (RADS),4 as well as gastroesophageal reflux disease (GERD).5 Dr. Carveth referred Knowlton to a speech and language pathologist to treat her vocal distortion. Dr. Carveth also noted that Knowlton had to be careful about what she ate due to the onset of new food allergies. Knowlton was prescribed Prilosec to treat the GERD symptoms.

In June of 2001, Fremont Compensation Insurance Company (Fremont), Wood River Medical Center's insurance company, requested Dr. Fullmer's opinion regarding Knowlton's exposure to sulfuric acid. Dr. Fullmer subsequently wrote a letter to Fremont explaining that Knowlton's initial diagnosis was an inhalation injury secondary to sulfuric acid exposure, but that the injury was mild or minor and would only be expected to last four to six weeks. He also explained that Knowlton likely reached maximum medical stability approximately six weeks after the exposure, and it was unlikely that her continued symptoms were directly related to the exposure. Rather, he believed her continued symptoms seemed more related to anxiety or a desire for a secondary gain related to the accident. Finally, he stated that he did not believe Knowlton had any significant physical impairment that was related to the industrial exposure.

Knowlton subsequently filed a complaint with the Industrial Commission, seeking reimbursement for her medical expenses and temporary total disability benefits. In the complaint, Knowlton named Wood River Medical Center6 and Fremont as defendants, and alleged that her exposure to toxic sulfuric acid fumes on September 12, 2000, caused her to suffer a chronic cough, dyspnea, laryngitis, RADS, and laryngospasm. Knowlton filed an amended complaint on May 12, 2003, this time seeking additional workers' compensation benefits in the form of permanent partial impairment benefits and permanent partial disability benefits. In the amended complaint, Knowlton also added dysfunctional larynx and epigastric reflux to the list of medical problems allegedly caused by the chemical exposure.

Defense counsel subsequently filed an answer on behalf of Wood River, as well as Cambridge Integrated Services, the successor in interest to Fremont, which had gone bankrupt at some point after Knowlton's complaint was filed. As a result of Fremont's bankruptcy, the Idaho Life and Health Insurance Guaranty Association (the Association)7 was added as an interested party in the litigation.8

At some point in 2002, Knowlton was awarded social security disability benefits as a result of her continued symptoms. The Social Security Administration determined that Knowlton's allegations with regard to her medical symptoms were credible based on objective medical findings.

For the next several years, Knowlton continued to see Dr. Carveth. Dr. Carveth maintained her diagnosis of RADS and noted that Knowlton was expressing significant anxiety and depression related to her illness, as well as her sister's unexpected death in a car accident. Knowlton continued to develop additional symptoms related to an expanding list of triggers, including dust, pollen, animal dander, industrial chemicals used in farm machinery maintenance, marking pens, smoke, grooming products, and consumption of alcohol and many foods. Knowlton also underwent an esophagogastroduodenoscopy (EGD). The test results showed inflammation at Knowlton's gastroesophageal junction, which is consistent with GERD.

In September of 2005, Knowlton was examined by several of Respondents' experts, including toxicologist Dr. Stephen Munday, allergist Dr. William Wallace, and psychologist Dr. Craig Beaver. Dr. Munday concluded that Knowlton did not meet the criteria for a RADS diagnosis, and her symptoms were more likely the result of a GERD condition. Dr. Wallace conducted a skin panel, testing for approximately 80 to 90 of the most common allergens and 6 of the major foods for which Knowlton had reported experiencing a reaction. All of the tests came back negative. Dr. Beaver concluded that there was a correlation between stressful events in Knowlton's life and the development of her physical symptoms.

For reasons not relevant to this appeal, a hearing on the merits of Knowlton's claim did not occur until June of 2008. At the hearing, the Referee heard live testimony from Knowlton, as well as the Respondents' toxicology expert, Dr. Munday. In addition to this testimony, the depositions of other witnesses, including several of Knowlton's family members, co-workers, and treating physicians, taken both before and after the hearing, were entered into the record. Each party submitted briefing on the matter at the close of the proceedings. Knowlton filed an opening brief and a reply brief, each totaling thirty pages. Respondents filed a motion to strike Knowlton's reply brief, arguing that Knowlton had failed to adhere to the page limitation set forth in the Commission's Judicial Rules of Practice and Procedure. The Referee denied the motion without commenting on the merits of Respondents' argument.

The Referee ultimately concluded that Knowlton had failed to demonstrate her medical symptoms were causally related to the chemical exposure she experienced on September 12, 2000, and that her symptoms were more consistent with GERD. Although the Referee determined Knowlton was not entitled to time loss benefits, or any form of disability benefits, the Referee did find that, because the medical treatment Knowlton received during the six weeks following the incident was a reasonable precautionary step taken in response to her exposure to an unknown chemical, she was entitled to compensation for those expenses.

The Commission adopted the Referee's findings of fact and conclusions of law. After the Commission denied Knowlton's motion for reconsideration, she timely appealed to this Court.

II.

Issues on Appeal

III.

Discussion

A. Standard of Review

When reviewing a decision by the Industrial Commission, this Court exercises free review over the Commission's conclusions of law, but will not disturb the Commission's factual findings if they are supported by substantial and competent evidence. I.C. § 72-732; Stewart v. Sun Valley Co., 140 Idaho 381, 384, 94 P.3d 686, 689 (2004). Substantial and competent evidence is "relevant evidence which a reasonable mind might accept to support a conclusion." Boise Orthopedic Clinic v. Idaho State Ins. Fund, 128 Idaho 161, 164, 911 P.2d 754, 757 (1996). The Commission's conclusions regarding the credibility and weight of evidence will not be disturbed unless they are clearly erroneous. Excell Constr., Inc. v. State, Dept. of Labor, 141 Idaho 688, 692, 116 P.3d 18, 22 (2005). This Court will not re-weigh the evidence or consider whether it would have drawn a different conclusion from the evidence presented. Id.

B. Causation

On appeal, Knowlton argues that there is no evidence in the record to support the Commission's determination that her symptoms were likely caused by GERD. Rather, Knowlton asserts that the testimony of her treating physicians, the testimony of her family members, friends, and co-workers, and the medical records, including the results of her methacholine challenge tests,9 all demonstrate that she contracted RADS as a result of the chemical exposure. Respondents, on the other hand, argue that the testimony of Dr. Munday, an expert in toxicology, and the testimony of Knowlton's treating physicians establish that Knowlton's symptoms were more consistent with GERD and could not have reasonably been caused by the chemical exposure.

A workers' compensation claimant has the burden of proving "to a reasonable degree of medical probability [that] the injury for which benefits are claimed is causally related to an accident occurring in the course of employment." Wichterman v. J.H. Kelly, Inc., 144 Idaho 138, 141, 158 P.3d 301, 304 (2007). "The issue of causation must be proved by expert medical testimony, although the Industrial Commission as the finder of fact may consider other evidence as well, including evidence regarding credibility." Id.

Although both parties presented testimony from numerous witnesses, the arguments in this case are largely based on the conflicting testimony of Knowlton's witness, Dr. Carveth, and Respondents' witness, Dr. Munday. Dr. Carveth testified that Knowlton developed RADS as a result of the chemical exposure, while Dr. Munday testified that Knowlton did not meet the criteria for a RADS diagnosis, and her symptoms were more likely the result of a GERD condition. In concluding that Knowlton had failed to prove her medical symptoms were causally related to the chemical exposure, the Commission gave greater weight to Dr. Munday's opinion, and agreed that Knowlton's symptoms were more consistent with GERD than RADS. The Commission also found that this conclusion was supported by the testimony and reports of Dr. Fullmer and Dr. Beaver. Because this Court gives great deference to the Commission's conclusions regarding the credibility and weight of evidence, the only issue before this Court is whether the evidence relied on by the Commission constitutes substantial and competent evidence.

The testimony and reports of Dr. Munday, Dr. Beaver, and Dr. Fullmer constitute substantial and competent evidence supporting the Commission's conclusion that Knowlton did not meet her burden of proving her symptoms were casually related to the chemical exposure. First and foremost, the Commission's conclusion is supported by the testimony of Dr. Munday, who specializes in treating patients who have been exposed to toxic chemicals, including sulfuric acid. Dr. Munday, after reviewing Knowlton's medical records, reviewing the hearing exhibits, and personally examining Knowlton, specifically concluded that Knowlton's symptoms were not likely caused by chemical exposure but, rather, were likely a result of a GERD condition.

Dr. Munday's first basis for reaching this conclusion was that the symptoms Knowlton first reported having on the day of the exposure were not consistent with someone who had been exposed to sulfuric acid. According to Dr. Munday, sulfuric acid is a highly water soluble chemical that is going to first affect the nose, throat, eyes, and upper airway upon exposure. Dr. Munday also mentioned that sulfuric acid would cause a "high degree of irritation" to these areas. For this reason, Dr. Munday was concerned about the symptoms Knowlton described on the day of the exposure.

Therefore, because Knowlton reported developing a headache and a sore throat on the day of the exposure and did not similarly report any irritation in her eyes or any significant irritation with her nose, Dr. Munday concluded her initial symptoms were not consistent with exposure to sulfuric acid.10

The Commission found Dr. Munday's report and testimony to be persuasive in this regard, pointing out that

The second basis for Dr. Munday's conclusion was that Knowlton is the only employee or person who was present at the hospital on the day of the incident who claims to have suffered any sort of residual symptoms or effects from the chemical exposure. According to Dr. Munday, this further supports the conclusion that Knowlton's symptoms were not a result of exposure to sulfuric acid.

The final basis for Dr. Munday's conclusion was that Knowlton's medical symptoms were more consistent with GERD rather than exposure to a chemical such as sulfuric acid. Dr. Munday explained that GERD can cause asthma-like symptoms similar to those Knowlton suffers from. Specifically, Dr. Munday's report indicates that,

Importantly, Knowlton was also diagnosed with severe GERD by Dr. Carveth.

In other words, Dr. Munday specifically reported that there is no medical evidence indicating that GERD is somehow caused by RADS.

Dr. Munday also thoroughly explained in his testimony and his report why he had concluded that Knowlton did not meet the criteria for a RADS diagnosis. The eight clinical criteria for diagnosing RADS include: (1) a documented absence of preceding respiratory complaints;11 (2) the onset of symptoms occurred after a single specific exposure incident or accident; (3) the exposure to a gas, smoke, fume, or vapor which was present in very high concentration and had irritant qualities to its nature; (4) the onset of symptoms occurred within 24 hours after the exposure and persisted for three months; (5) symptoms simulated asthma with cough, wheezing and dyspnea; (6) pulmonary function tests may show airflow obstructions; (7) methacholine challenge test was positive; and (8) other types of pulmonary diseases were ruled out. Dr. Munday conceded that Knowlton developed symptoms immediately following the chemical exposure and that her symptoms persisted for more than three months, but disputed that the overall medical evidence, Knowlton's medical history, and Knowlton's symptoms indicated she was suffering from RADS.

First, Dr. Munday explained that patients generally do not develop RADS unless they have suffered "extensive high-dose exposure to highly irritating agents." He did mention that there has been some discussion in the medical community regarding whether low or intermediate doses could cause the syndrome, but explained that such a conclusion is controversial and not widely supported. For this reason, Dr. Munday found that the fact that Knowlton had not been exposed to a high dose of chemical,12 militated against a RADS diagnosis.

Next, Dr. Munday also concluded that Knowlton was not suffering from RADS because she continued to have normal, or near-normal, pulmonary functioning tests. Dr. Munday testified that nearly all of the spirometry tests13 produced normal results, and those that produced abnormal results were so near normal that they were unimportant. In fact, Dr. Munday explained that the normal breath ranges have recently been broadened and Knowlton's abnormal tests would now likely be classified as normal. Knowlton relies heavily on the results of the methacholine tests conducted by Dr. Fullmer and Dr. Carveth to support her argument that the Commission erred in concluding she had not demonstrated she was suffering from RADS as a result of the chemical exposure. The results of the methacholine tests showed a moderate degree of airway hyperresponsiveness. However, Dr. Munday testified that although this type of testing is an effective way to rule out asthma in a patient, positive results must be interpreted in the appropriate setting because false positives frequently occur.14 He mentioned that ten to twenty percent of people have a positive result, even if they do not suffer from asthma. Dr. Munday also explained that the results of the methacholine tests were not helpful in determining causation because whether a person is experiencing respiratory problems as a result of allergies, RADS, or GERD, the tests do nothing to demonstrate which one is the cause.

Finally, Dr. Munday determined that many of Knowlton's symptoms were not attributable to RADS. Specifically, Dr. Munday explained that the vocal cord dysfunction, the odor-induced symptoms, and the subsequent development of allergic reactions to various foods were not characteristic of someone suffering from RADS. He opined that Knowlton's negative reaction to odors may be a result of psychosomatic odor intolerance. In reaching this conclusion, Dr. Munday found it important that all of Knowlton's allergy tests were negative. Dr. Munday also pointed out that there is no valid scientific evidence that would support an association between exposure to sulfuric acid and the subsequent development of an allergy to other sulfa-containing products. In other words, Knowlton's concern that she was developing an allergy to foods containing sulfa as a result of the exposure to sulfuric acid is not medically supportable. As mentioned above, Dr. Munday testified that Knowlton's symptoms, especially the vocal cord dysfunction, were more consistent with GERD, and there is no medical evidence that GERD is somehow caused by RADS.15

The Commission's conclusion is also supported by the testimony of Dr. Fullmer and Dr. Beaver. Both Dr. Fullmer and Dr. Beaver testified that Knowlton's symptoms were likely attributable to her emotional distress rather than to the chemical exposure. Dr. Fullmer explained that, while Knowlton's initial diagnosis was an inhalation injury secondary to sulfuric acid exposure, the injury was mild or minor and would only be expected to last four to six weeks. He explained that he did not believe Knowlton suffered any significant physical impairment related to the exposure after the six-week mark, and that it was more likely that her symptoms were related to anxiety or a desire for secondary gain. Finally, he stated that he did not believe Knowlton had any significant physical impairment that was related to the industrial exposure. Similarly, Dr. Beaver concluded that there was a strong correlation between stressful events in Knowlton's life and the development of her physical symptoms. Although Dr. Beaver testified that he could not say that Knowlton did not have any respiratory difficulties, he did testify that there was a "conditioned relationship" between her emotional distress and her respiratory difficulties.

The testimony and reports of these medical professionals constitute substantial and competent evidence supporting the Commission's decision. In support of her argument that the Commission erred, Knowlton points to conflicting evidence and testimony in the record. However, this Court is not in the position to re-weigh evidence or determine whether it would have reached a different conclusion. Knowlton's main focus on appeal appears to be the temporal link between the chemical exposure and her medical symptoms. While the temporal connection certainly supports Knowlton's position, such a connection alone does not establish that her symptoms were caused by the chemical exposure. The medical evidence relied on by the Commission indicates that many of Knowlton's continued symptoms are inconsistent with a RADS diagnosis. Therefore, the Commission's determination that Knowlton did not meet her burden of proving her symptoms were related to the chemical exposure is supported by substantial and competent evidence.

Although the Commission's ultimate conclusion is supported by substantial and competent evidence in the record, its discussion regarding Knowlton's credibility is of some concern. The Referee made the following findings of fact with regard to Knowlton's credibility:

These credibility findings were adopted by the Commission.

Determining the credibility of witnesses and evidence is a matter within the province of the Commission. Stevens-McAtee v. Potlatch Corp., 145 Idaho 325, 331, 179 P.3d 288, 294 (2008). However, such findings are still subject to review by this Court. When analyzing the Commission's findings regarding credibility, this Court has bifurcated the issue into two categories, "observational credibility" and "substantive credibility." Painter v. Potlatch Corp., 138 Idaho 309, 313, 63 P.3d 435, 439 (2003). Observational credibility "goes to the demeanor of the appellant on the witness stand and it requires that the Commission actually be present for the hearing in order to judge it." Id. In contrast, substantive credibility "may be judged on the grounds of numerous inaccuracies or conflicting facts and does not require the presence of the Commission at the hearing." Id. The Court will not disturb the Commission's findings regarding credibility if the findings are supported by substantial and competent evidence. Id.

In this case, it does not appear from the record that the Referee had any reason to doubt Knowlton's credibility. Knowlton's explanation of the events leading up to, and following, the incident on September 12, 2000, has been consistent. Although the Referee is correct that some details have been forgotten over the eight years leading up to the hearing, such is to be expected. However, the fact that Knowlton at times had difficulty remembering certain details does not support the Commission's conclusion that Knowlton's testimony could "not be accepted at face value." Interestingly, the Referee in this case is the same Referee that presided over the hearing in Stevens-McAtee v. Potlatch Corp. In that case, the Referee held that the claimant's testimony was not credible because the claimant "improved" or "enhanced" his testimony by adding specific details at the hearing. Stevens-McAtee, 145 Idaho at 329, 179 P.3d at 292. On appeal, this Court found that the Referee's findings with regard to the claimant's credibility were not supported by substantial and competent evidence because, although there may have been slight differences or additions at the hearing, the claimant's testimony regarding how he was injured had remained consistent, and any differences in his testimony did not support the Referee's conclusion that he was not credible. Id. at 331, 179 P.3d at 294. Similarly in this case, the differences or additions in Knowlton's testimony over the eight years preceding the hearing does not support the Referee's conclusion that Knowlton was not credible. Therefore, the Commission's conclusions with regard to Knowlton's credibility are not supported by substantial and competent evidence, and this Court is not required to accept them on appeal. Nonetheless, because the issue of causation is dispositive on appeal and does not take into account the Referee's unsupported determination that Knowlton was not credible, this Court affirms the Commission's decision to deny Knowlton workers' compensation benefits, other than to cover the medical expenses incurred during the six weeks following the incident. Because we affirm the Commission's determination that Knowlton failed to meet her burden of proving her symptoms are causally related to the chemical exposure, it is unnecessary for us to consider the other issues raised by the Respondents on appeal, including whether the Commission has jurisdiction to order the Association to pay Knowlton workers' compensation benefits and whether the Commission erred in denying the Respondents' motion to strike.

C. Attorney Fees for the Proceedings Before the Commission

Knowlton argues that if this Court finds that the Commission erred in denying her claim, the Commission abused its discretion by failing to award her attorney fees incurred during the proceedings before the Commission pursuant to I.C. § 72-804. I.C. § 72-804 authorizes attorney fees to be paid to a claimant, where the employer or surety contests a claim for compensation without reasonable grounds to do so. I.C. § 72-804. Because there is substantial and competent evidence to support the Commission's decision, the Commission did not abuse its discretion in failing to award Knowlton attorney fees.

D. Attorney Fees on Appeal

Knowlton also contends that she is entitled to an award of attorney fees on appeal pursuant to I.C. § 72-804 and I.A.R. 41 because Respondents denied her claim and refused to pay benefits without reasonable grounds. Because we affirm the Commission's decision to deny Knowlton's claim for additional workers' compensation benefits, Knowlton is not entitled to attorney fees on appeal.

Respondents request attorney fees on appeal pursuant to I.A.R. 41 and 11.216 on the ground that Knowlton frivolously pursued this appeal. I.A.R. 11.2 allows the Court to order a party, or a party's attorney, to pay attorney fees as a sanction for pursuing an appeal that is (1) not well grounded in fact; (2) not warranted by existing law or a good faith argument for the extension, modification, or reversal of existing law; or (3) was pursued for an improper purpose. Respondents argue that attorney fees are warranted because, on appeal, Knowlton has unreasonably sought to dispute the Commission's factual findings by pointing to irrelevant conflicts in the evidence. Although we affirm the Commission's ultimate conclusion, Knowlton's appeal was not frivolously pursued such that sanctions are warranted against either Knowlton or her counsel.

IV.

Conclusion

There is substantial and competent evidence in the record to support the Commission's conclusion that Knowlton failed to demonstrate her medical problems were causally related to the chemical exposure at Wood River Medical Center. Thus, this Court affirms the Commission's determination that Claimant is only entitled to workers' compensation benefits for the medical expenses incurred during the six weeks following the exposure. Costs, but no attorney fees, are awarded to Respondents.

Chief Justice EISMANN, and Justices BURDICK, W. JONES and HORTON concur.