--- title: "Dermatology Expert Not Allowed to Opine on DMDM-induced Dermatitis" meta: "og:description": "While the dermatology expert is qualified to opine on the ability of DMDM to cause dermatitis, his opinion here is grounded in insufficient facts and data" "og:title": "Dermatology Expert Not Allowed to Opine on DMDM-induced Dermatitis" author: "Shuva Guha Thakurta" description: "While the dermatology expert is qualified to opine on the ability of DMDM to cause dermatitis, his opinion here is grounded in insufficient facts and data" --- # Dermatology Expert Not Allowed to Opine on DMDM-induced Dermatitis Posted on August 3, 2026 by Shuva Guha Thakurta Plaintiff Zebin Hossain brought this action against Defendant Unilever United States, Inc., alleging that she suffered hair loss as a result of an allergic reaction to a preservative contained in TRESemmé Keratin Smooth shampoo, a Unilever product. The shampoo contains a preservative known as DMDM hydantoin ("DMDM"). DMDM is a formaldehyde donor, a preservative that works by releasing small amounts of formaldehyde over time. Plaintiff alleged that DMDM may trigger an allergic reaction in some individuals that leads to dermatitis. Plaintiff proffered one expert in support of her claims, Dr. [Marc J. Serota](https://expertwitnessprofiler.com/expert-witness/Marc-Serota/1542173). Defendant contended that Plaintiff cannot meet her burden to establish that Serota's opinion is reliable because Serota (1) formed his opinion without conducting diagnostic procedures normally performed by dermatologists outside of the litigation context, (2) ignored facts that contradicted his causation theory, (3) failed to conduct any tests that would confirm or refute his theory, and (4) did not rule out other potential causes of Plaintiff's hair loss. ![Dermatology Expert Not Allowed to Opine on DMDM-induced Dermatitis](https://media.jurimatic.com/images/blog_pic_640X480_2026_08_03T200114_366.webp) ## **Dermatology Expert Witness** Dr. [**Marc Jonathan Serota**](https://expertwitnessprofiler.com/expert-witness/Marc-Serota/1542173) is triple board-certified in dermatology, pediatrics, and allergy and immunology. Serota is recognized as a national expert in dermatology and allergy topics. He also frequently lectures across the country and has published numerous articles in his areas of expertise. [**Want to know more about the challenges Marc Serota has faced? Get the full details with our Challenge Study report**](https://expertwitnessprofiler.com/order/add?eId=1542173&pId=3). ## **Discussion by the Court** Serota's general causation methodology involved a review of "dozens of peer-reviewed medical and scientific articles and studies" combined with his "experience as a practicing dermatologist." From this information, Serota concluded that DMDM "commonly causes contact dermatitis." Serota employed a similar methodology to conclude that "dermatitis of the scalp can cause hair loss," grounding his opinion in medical literature and his own personal experience as a practitioner. Serota's theory proceeds in two steps. First, he explained that contact with products containing DMDM can cause dermatitis where a person is allergic to DMDM (allergic contact dermatitis), or where a person is in contact with a sufficiently large amount of DMDM for a sufficiently long period of time (irritant contact dermatitis). Second, he said that dermatitis can lead to hair loss. Serota opined that this sequence of events is what happened to Plaintiff. In other words, the theory underpinning Serota's opinion requires that Plaintiff had a reaction to the DMDM in the shampoo and that reaction led to dermatitis-induced hair loss. ### _Analysis_ Serota failed to confirm or rule out whether Plaintiff had any allergies at all and ignored the fact that her medical records contained neither evidence of allergies nor dermatitis. Further, Serota's deposition testimony contradicts the conclusion in his report that Plaintiff suffered from dermatitis. And contrary to Plaintiff's assertion, he did not rule out at least one other obvious potential cause of hair loss, namely the fact that Plaintiff dyed her hair regularly during the relevant time period. Accordingly, Serota is "unable to tie his conclusion to the facts presented by this case," leaving "too great an analytical gap between the data and the opinion proffered" for it to be admissible. Serota conducted no diagnostic testing to determine whether or not Plaintiff had a DMDM allergy. While Plaintiff is correct that "an expert does not need to conduct every diagnostic test to assert a reliable causation opinion _if the opinion is based on other forms of reliable diagnostic data_," Serota did not, and indeed could not, rely on diagnostic testing performed by other medical professionals. That is because Plaintiff "has never been tested for any allergies." Plaintiff tries to minimize this fact by pointing out that she "was not experiencing active hair loss when Serota was performing his work on this case," but that does not explain why he failed to even offer her a patch test when that was his practice in the "normal course" of treating patients. First, Plaintiff's medical records and medical history indicated no signs of any allergies or dermatitis. Second, Serota's deposition testimony calls into question whether he did in fact review "numerous scalp and hair photos." During his deposition, Serota was presented with photographs depicting Plaintiff's scalp while she was actively using TRESemmé shampoo and which, by her own admission, depicted the full extent of her scalp irritation. Serota testified that those pictures did not show any signs of dermatitis, and that he "would argue against" a finding of dermatitis based on the pictures if they had been taken "within 48 hours or so" of using the shampoo. As it turns out, those photos were taken "within 48 hours or so" of Plaintiff washing her hair with the shampoo. Given that these photographs reflected the full extent of Plaintiff's scalp irritation, and the fact that at this time Plaintiff "washed her hair with TRESemmé every other day," it is difficult to reconcile Serota's observation that the photographs reflected no signs of "inflammation", "rash", "scaling", or—crucially—"dermatitis", with his opinion that "in this case DMDM triggered a dermatitis leading to alopecia." Plaintiff tries to minimize this as a "minor" oversight that is "immaterial." But that cannot be true given that the entire basis for Serota's opinion is that Plaintiff's hair loss was triggered by DMDM-induced dermatitis. The Court found that Serota failed to conduct tests that would have bolstered his theory and disregarded facts that undermined it, including the diagnoses of other medical providers. His opinion is largely based on Plaintiff's self-reported narrative and a timeline that is, at best, suggestive of a correlation between when she began using TRESemmé and when she began losing her hair. Put differently, his opinion is not "based on sufficient facts" nor is it "the product of reliable principles and methods" as is required by [Rule 702](https://www.law.cornell.edu/rules/fre/rule_702#:~:text=Rule%20702%20sets%20forth%20the,is%20a%20relatively%20narrow%20inquiry.). ## **Held** The Court granted Defendant's motion to preclude the testimony of Marc J. Serota. ## **Key Takeaway** Reliability within the meaning of Rule 702 requires a sufficiently rigorous analytical connection between that methodology and the expert's conclusions. Indeed any step that renders the analysis unreliable under the [_Daubert_](https://www.law.cornell.edu/wex/daubert_standard) factors renders the expert's testimony inadmissible. ## **Case Details:** | Case Caption: | Zebin Hossain v. Unilever U.S. Inc. | | --- | --- | | Docket Number: | 1:21cv2833 | | Court Name: | United States District Court for the Eastern District of New York | | Order Date: | July 30, 2026 | --- ## **You Might Also Like** ![Dermatology Expert Not Allowed to Opine on DMDM-induced Dermatitis](https://media.jurimatic.com/images/blog_pic_640X480_2026_08_03T200114_366.webp) [**Dermatology Expert Not Allowed to Opine on DMDM-induced Dermatitis**](https://expertwitnessprofiler.com/dermatology-expert-not-allowed-to-opine-on-dmdm-induced-dermatitis/dermatology-expert-not-allowed-to-opine-on-dmdm-induced-dermatitis)![Hospitality Expert Not Allowed to Opine on Food Safety Regulations](https://media.jurimatic.com/images/blog_pic_640X4802.webp) [**Hospitality Expert Not Allowed to Opine on Food Safety Regulations**](https://expertwitnessprofiler.com/dermatology-expert-not-allowed-to-opine-on-dmdm-induced-dermatitis/hospitality-expert-not-allowed-to-opine-on-food-safety-regulations)![Emergency Management Expert Allowed to Opine on Public Safety Communications](https://media.jurimatic.com/images/blog_pic_640X480_2026_07_31T200905_3121.webp) [**Emergency Management Expert Allowed to Opine on Public Safety Communications**](https://expertwitnessprofiler.com/dermatology-expert-not-allowed-to-opine-on-dmdm-induced-dermatitis/emergency-management-expert-allowed-to-opine-on-public-safety-communications)![Law And Legal Expert Allowed to Opine on the Standard of Care for a Certified Financial Planner](https://media.jurimatic.com/images/blog_pic_640X480_2026_07_31T175244_408.webp) [**Law And Legal Expert Allowed to Opine on the Standard of Care for a Certified Financial Planner**](https://expertwitnessprofiler.com/dermatology-expert-not-allowed-to-opine-on-dmdm-induced-dermatitis/law-and-legal-expert-allowed-to-opine-on-the-standard-of-care-for-a-certified-financial-planner)![Aviation Maintenance Expert Was Not Allowed to Opine on Agency Relationship ](https://media.jurimatic.com/images/blog_pic_640X480_2026_07_30T195621_2651.webp) [**Aviation Maintenance Expert Was Not Allowed to Opine on Agency Relationship **](https://expertwitnessprofiler.com/dermatology-expert-not-allowed-to-opine-on-dmdm-induced-dermatitis/aviation-maintenance-expert-was-not-allowed-to-opine-on-agency-relationship-)