Methylisothiazolinone (MI) allergy
Contact allergy to MI preservative in wet wipes and cosmetics.
About methylisothiazolinone (mi) allergy
Methylisothiazolinone, usually shortened to MI, is a preservative added to wet wipes, cosmetics, shampoos, liquid soaps, household cleaners and some paints and glues. Its increased use over the past decade led to a well-documented rise in contact allergy. Allergy to MI is a delayed, type IV allergic contact dermatitis, so the rash typically appears 12 to 72 hours after contact. It is now one of the more frequent causes of preservative allergy, and can affect anyone using leave-on or rinse-off products, with parents sometimes sensitised through frequent use of baby wipes.
The rash is itchy and red, often scaly or blistered, appearing where the product touched the skin, commonly the face, hands, and the buttock or nappy area with wipes. Airborne exposure from freshly painted rooms can cause facial and eyelid dermatitis without direct contact. MI is closely related to methylchloroisothiazolinone (MCI), and people usually react to both.
Diagnosis is by patch testing with a dermatologist, not skin-prick testing. Management means reading labels carefully and avoiding products containing MI and MCI, choosing preservative systems that suit sensitised skin, and being cautious around fresh paint. Emollients support recovery and topical steroids may be advised for flares. See your GP or a dermatologist if a facial, hand or nappy-area rash keeps returning or you need help identifying the source.
Common triggers
- Methylisothiazolinone (MI) and products containing it
Symptoms
- Red, itchy rash (contact dermatitis)
- Dry, cracked or scaly skin
- Blistering or weeping in severe cases
- Burning or stinging where skin met the trigger
Avoidance & management
- Avoid skin contact with the trigger
- Wear gloves or use barrier creams
- Choose products labelled free from the allergen
- Rinse skin promptly after contact
- Use emollients or prescribed steroid creams
Sources & references
Allergy safety: what everyone should know
Mild-to-moderate reaction signs
- Itching, hives or a raised rash
- Swelling of lips, face or eyes
- Tingling mouth, sneezing, runny nose
- Stomach pain, nausea or vomiting
Anaphylaxis — call 999 (UK) or 112 (EU) immediately
- Difficult or noisy breathing, wheeze, persistent cough
- Swelling of the tongue or tightness in the throat
- Dizziness, collapse, pale and floppy (young children)
- Use an adrenaline auto-injector (e.g. EpiPen) at once if prescribed, then call an ambulance even if symptoms improve
Allergy or intolerance? A true allergy involves the immune system and can escalate quickly; an intolerance (e.g. lactose intolerance) is unpleasant but not life-threatening. The symptoms overlap, so self-diagnosis is unreliable.
Getting tested: home-testing kits based on IgG are not diagnostically valid. If you suspect an allergy, ask a GP for referral to an allergy clinic for skin-prick or specific-IgE testing and a supervised food challenge where appropriate.