Contact allergy to products with methylisothiazolinone; plus, topical options for...

Household and personal care products are common sources of contact allergy in dermatology patients. Dr. Vincent DeLeo talks with Dr. Amber Atwater and Dr. Margo Reeder and about the epidemic of allergic contact dermatitis associated with methylisothiazolinone (MI), a common preservative found in many water-based products. Dr. Reeder and Dr. Atwater discuss the emergence of MI as a contact allergen and highlight some of the common and lesser-known sources of MI exposure.

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3. Dr. Andrew Alexis discusses topical treatment options for pigmentary disorders

Things you will learn in this episode:
- Methylisothiazolinone (MI) has been used for decades as a preservative in combination with methylchloroisothiazolinone; however, higher concentrations of MI alone have been used in personal care products beginning in the 2000s: “That’s really when we began to see patients being exposed to MI and subsequently developing contact allergy,” notes Dr. Reeder.
- Common sources of MI exposure include liquid and water-based products such as dish soaps, shampoos, household cleaners, hair conditioners and dyes, laundry products, and soaps and cleansers.
- Latex-based paints containing MI can result in airborne contact dermatitis from off-gassing when the paint is curing on the wall.
- Another common source of MI contact dermatitis is slime, a sticky play substance that children concoct out of household products such as glue or cleaning agents that contain MI.
- Contact allergy to MI may present in a photodistributed pattern and also has been associated with photoaggravation. Patients also may demonstrate lasting photosensitivity even when avoiding the allergen; therefore, it is important to consider including MI when performing photopatch testing.
- Two additional potentially allergenic isothiazolinones found in household products and industrial chemicals include benzisothiazolinone and octylisothiazolinone.
- The T.R.U.E. Test includes MI in a mix with methylchloroisothiazolinone but not on its own, which has been known to miss a considerable number of patients who are allergic to MI; therefore, patch testing to MI alone may be beneficial in patients with allergic contact dermatitis who test negative for MI contact allergy using the T.R.U.E. Test.
- Many patients are sensitized to MI when it is used in leave-on products. The European Union has banned MI from use in these products, but currently there are no regulations in the United States.

Hosts: Elizabeth Mechcatie, Terry Rudd, Vincent A. DeLeo, MD (Keck School of Medicine of the University of Southern California, Los Angeles)

Guests: Margo Reeder, MD (University of Wisconsin, Madison); Amber Reck Atwater, MD (Duke University, Durham, North Carolina); Andrew F. Alexis, MD, MPH (Icahn School of Medicine at Mount Sinai, New York.

Show notes by Alicia Sonners, Melissa Sears, and Elizabeth Mechcatie.

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