What are Preservative Sensitizers?
Preservatives are essential ingredients that prevent bacterial and fungal growth in cosmetics, extending shelf life. However, certain preservatives — particularly Methylisothiazolinone (MI), Methylchloroisothiazolinone (MCI), and formaldehyde-releasing preservatives — are potent skin sensitizers that have caused widespread allergic reactions.
The rise in MI/MCI allergies was so dramatic that dermatologists called it an "epidemic." Cases of MI allergy increased by 500% between 2010-2015 in Europe.
Where are they found?
Preservatives are in virtually all water-based cosmetics and personal care products. If a product contains water and sits on a shelf, it almost certainly contains preservatives.
Why do people avoid them?
MI and MCI became notorious allergens in the 2010s. Their widespread use in cosmetics and household products led to what dermatologists called an "epidemic of contact allergy." The EU responded by restricting MI in leave-on products (2015) and rinse-off products (2017).
Formaldehyde releasers (DMDM Hydantoin, Imidazolidinyl Urea, Quaternium-15) slowly release formaldehyde — a known carcinogen and one of the most potent contact allergens known.
MI/MCI allergies can cause reactions so severe they may be mistaken for burns. If you've developed sudden, unexplained facial dermatitis, check your products for these preservatives.
In Indian Products 🇮🇳
Many Indian brands still use MI/MCI combinations that have been restricted in Europe. The preservative combination known as "Kathon CG" (MI + MCI) is still common. DMDM Hydantoin is widely used in Indian shampoos — internationally, it's the subject of class-action lawsuits alleging hair loss.
Brands to check: TRESemmé (India), Pantene, and various domestic brands. Look specifically for "Kathon" or "DMDM Hydantoin" on labels.
How to check your products
Scan ingredient lists carefully. These preservatives have many names and can be listed in abbreviated forms.
If you've suddenly developed facial eczema or rashes, check your wet wipes, hand sanitizer, and leave-on products first — these are the most common MI/MCI culprits.
Safer Alternatives
Safer preservative alternatives include Phenoxyethanol (well-tolerated by most), Sodium Benzoate + Potassium Sorbate (food-grade), and Ethylhexylglycerin. Some "preservative-free" products use airtight packaging instead.