Commonly advised againstPreservative

Methylisothiazolinone (MI/MCI) in personal lubricant

MI and its chlorinated partner MCI caused a well-documented epidemic of contact allergy after they replaced parabens in leave-on products, and the EU has since restricted them sharply in leave-on cosmetics. Once you are sensitised, the reaction is durable — on mucosal tissue that is an unpleasant thing to discover.

Look for instead: Phenoxyethanol, sodium benzoate, or potassium sorbate preservative systems.

At a glance

Role in the formula
Preservative
Osmolality
Not an osmolality driver
Rating
Commonly advised against — Has a well-documented downside for intimate use; most guidance suggests choosing a formula without it.
Label names to look for
methylisothiazolinone, methylchloroisothiazolinone

Matters more if: sensitive or irritation-prone.

Care signal

A rash, swelling, or persistent burning after contact deserves a clinician's assessment, not a retry.

Care-first checklistTelehealth & clinical care options

Common questions

Is methylisothiazolinone (mi/mci) a problem in a lubricant?

Most guidance suggests choosing a formula without it for intimate use. MI and its chlorinated partner MCI caused a well-documented epidemic of contact allergy after they replaced parabens in leave-on products, and the EU has since restricted them sharply in leave-on cosmetics. Once you are sensitised, the reaction is durable — on mucosal tissue that is an unpleasant thing to discover.

What does methylisothiazolinone (mi/mci) do in the formula?

Its role is preservative. Has a well-documented downside for intimate use; most guidance suggests choosing a formula without it.

What should I look for instead?

Phenoxyethanol, sodium benzoate, or potassium sorbate preservative systems.

Does the specific product still matter?

Yes. An ingredient list shows what is in a formula, never how much, and two products sharing an ingredient can behave completely differently. The product's own label and instructions always take priority over a general category rating.

Next steps

Gentle comfort checklistCheck a full labelCare-first checklist

Related ingredients

Educational information about ingredient categories only — not medical advice, not a product-safety verification, and not a claim that any formula is safe or unsafe for your body. An ingredient list shows what is in a product, never how much. A product's own label and instructions always take priority. Stop and seek care for pain, bleeding, allergic reaction, or worsening symptoms.