Your red, dry hands may be the result of using dishwashing liquid that contains a common preservative, or it may be causing your itchy face or scalp if it’s in your moisturizer or shampoo.
The preservative, methylisothiazolinone (MI), won an award in 2013 from the American Contact Dermatitis Society for making the biggest impact on the general public. And it seems there’s no stopping its impact: A Danish study of 1,511 participants, published in the April 2014 issue of Dermatitis, found that the percentage of people who had a reaction to MI on specialized skin testing increased from 4.8 in 2011 to 6.5 in 2013.
Symptoms of an MI allergy include burning, itching, and redness that most commonly occurs on the hands, face, genital or anal area, arms and legs—parts of the body that regularly come into contact with personal care and household products.
From 2007 to 2010, the number of beauty products containing higher concentrations of MI more than doubled to 2,400 in the United States, possibly one reason the incidence of reactions is increasing.
MI, often used in combination with another common allergen, methylchloroisothiazolinone (MCI), is found in personal care products like cosmetics; nail polish and remover; sunscreen; hair products; bath products such as soap, cleansers, bubble bath, and moisturizers; deodorant and shaving products; baby products such as oil, powders, lotion and creams; and moist wipes, towelettes, and toilet paper. They’re also found in common household goods (including “green” products) such as laundry detergents, stain removers, fabric softeners, and glass and wood cleaners as well as in paints, varnishes, and inks.
To determine whether MI or another allergen is causing a skin reaction, allergists perform a specialized type of skin testing called a patch test. Suspected allergens are applied to patches and placed on your skin (usually your back or arm) for 48 hours. After that time, your doctor checks for skin irritation at the patch site, which indicates an allergic reaction.
If you’re allergic to MI, avoid products containing the preservative. Not all products are labeled with full ingredient lists, so it can be difficult to tell which items contain MI, but you may be able to find full lists online. Since MI is a derivative of the chemical compound isothiazolinone, you may also want to avoid products containing that preservative as well as another derivative, chloromethylisothiazolinone.