I’m used to battling dry, itchy skin in the winter months, but a few weeks back, I had an unusual reaction to my favorite moisturizer. I broke out in hives and couldn’t stop scratching. I’d been using this cream for years with no issue, so I contacted my physician just to be safe. She said that the probable culprit was a methylisothiazolinone, or MI, allergy. According to her, MI is an ingredient in a surprising number of skincare and household products.
As it turns out, this allergy is fairly common. What exactly is this chemical, and what are the products that contain it?
What is methylisothiazolinone?
According to the FDA, methylchloroisothiazolinone (MI), which is often combined with methylchloroisothiazolinone (MCI) in skincare, cosmetics, and cleaning products, is a “standardized chemical allergen.” This chemical compound forms a preservative that keeps products from growing bacteria and fungus. In high concentrations, it can cause chemical burns and severe skin irritation.
When I expressed confusion as to why I’d never heard of this ingredient or experienced a reaction to it before, my doctor explained that because MI is in so many products, my sudden allergic reaction was likely the result of sensitization, which happens when your immune system gets so used to a product that it develops antibodies to it. These antibodies cause a defensive response, and boom! There’s your allergic reaction.
What products contain MI?
MI is found in many everyday cosmetic products, including shampoo, sunscreen, eyeliner, soap, nail polish, and more. It’s also in a bunch of household products, like paint, glue, laundry detergent, fabric softener, and cleaning solutions.
If you’re wondering how to avoid such a common ingredient, visit EWG.org, which has useful information about certain chemicals and ingredients, as well as guidance on product safety. There are a number of good quality “clean” beauty and cleaning products on the market these days, which don’t have MI in their ingredient list. Just check those labels!
Symptoms and Treatment for MI allergy
Always contact your physician and make an appointment if you can. Resist the temptation to self-diagnose, and be on the lookout for a rash. This rash could show up on the face, hands, scalp, neck, and limbs. To help ease your discomfort, your doctor might suggest an over-the-counter antihistamine or a steroid cream. If your itching or irritation is severe, they might prescribe a stronger topical agent to help calm your skin.
If you have an allergic response to MI, avoid products that list the following ingredients:
If you have sensitive, allergy-prone skin, look for cleaning products that are more natural and have fewer ingredients (Skout’s Honor is a great one, if you’re cleaning up after pets!). I recently switched to clean cosmetics, and I don’t regret it. Nothing is worth having my skin uncomfortably itchy or irritated!
Are you suffering from dry, itchy skin this winter? It might be worth checking with your doctor about whether you could be experiencing an MI allergy.
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