Sensitizing , Preservatives

Preservative that’s generally recommended for use only in rinse-off products such as cleansers or shampoos. Although used in leave-on products, methylisothiazolinone is known to be sensitizing when used in leave-on products.

As with most ingredients with problematic potential, much depends on the amount used, but, as a general rule, if you see methylisothiazolinone in the middle of an ingredient list for a leave-on product, you should avoid it. Its use in both rinse-off and leave-on cosmetics products is restricted to low amounts as a means to avoid sensitivity while maintaining its efficacy as a preservative, but even in the low amount permitted (0.01%) has raised questions about it being more sensitizing than most other preservatives. 

References for this information:

Anais Brasileiros de Dermatologia, 2014, issue 3, page 527

Cosmetics & Toiletries, 2014, issue 2, page 24

See preservatives , methylchloroisothiazolinone

«Back to Ingredient Dictionary

About the Experts

Paula Begoun is the best-selling author of 20 books on skin care and makeup. She is known worldwide as the Cosmetics Cop and creator of Paula's Choice. Paula's expertise has led to hundreds of appearances on national and international television including:

View Media Highlights

The Paula's Choice Research Team is dedicated to busting beauty myths and helping you solve your skincare frustrations with research-supported expert advice—so you'll have the facts you need to take the best possible care of your skin.

Skip to Top of Page
[{"Key":"SpecialOffers","Name":"SpecialOffers","BrontoID":"0bbf03e9000000000000000000000000ead0","Label":"Web Specials & Daily Deals","DisplayDescription":"","DisplayRestrictions":"","Value":null},{"Key":"SpecialOffersLessFrequent","Name":"SpecialOffersLessFrequent","BrontoID":"0bbf03e90000000000000000000000012122","Label":"Web Specials","DisplayDescription":"","DisplayRestrictions":"Less Frequent","Value":null},{"Key":"BeautypediaExclusives","Name":"BeautypediaExclusives","BrontoID":"0bbf03e9000000000000000000000000eace","Label":"Beauty Exclusives","DisplayDescription":"Expert Advice Newsletter ","DisplayRestrictions":"twice a month","Value":null},{"Key":"BeautypediaUpdates","Name":"BeautypediaUpdates","BrontoID":"0bbf03e9000000000000000000000000ead1","Label":"Beautypedia Updates","DisplayDescription":"New reviews on Beautypedia ","DisplayRestrictions":"twice a month","Value":null}]


Paula’s Choice Auto Delivery is a quick and convenient way to make sure you never run out of your favorite products again. Just select the products you can’t live without, choose how often you’d like them delivered and we’ll take care of the rest.

Get 10% off your first order when you sign up today.