From 4-Legger® - Makers of 4-Legger USDA Certified Organic Dog Shampoo

Is Methylisothiazolinone Safe for Dogs

The Hidden Dangers of Methylisothiazolinone and Methylchloroisothiazolinone in Pet Shampoo

We often take for granted that the ingredients in pet shampoo are all safe and gentle.

Many of the manufacturers who develop pet shampoo include Methylisothiazolinone (MIT) and Methylchloroisothiazolinone (CMIT) in their ingredients. 

Let's explore what MIT and CMIT are, how they can be contaminated, and why they are dangerous for long-term use on dogs.

What Are MIT and CMIT?

Methylisothiazolinone (MIT) and Methylchloroisothiazolinone (CMIT) are synthetic preservatives commonly used in personal care and pet grooming products. They are primarily added to these products to inhibit the growth of bacteria, fungi, and yeast, extending their shelf life. They are known for their antimicrobial properties and are effective at low concentrations.

How MIT and CMIT Can Be Contaminated

MIT and CMIT can become contaminated with other substances during the manufacturing process or when they are added to products. Contamination can occur due to impurities, by-products, or reactions with other chemicals present in the formulation. The most concerning contaminants in these compounds are formaldehyde and acetaldehyde, which are known to be potentially carcinogenic.

The Danger of Long-Term Use on Dogs

When applied to dogs, products containing MIT and CMIT can lead to several health concerns, especially with long-term use:

  1. Skin Irritation: MIT and CMIT are strong sensitizers and can lead to skin irritation, rashes, and redness in dogs. Pets with sensitive skin may be particularly susceptible to these effects.

  2. Allergic Reactions: Allergic reactions can range from mild itching to severe allergic dermatitis. Prolonged exposure to MIT and CMIT can increase the risk of sensitization and allergic reactions in dogs.

  3. Toxicity: Ingesting or licking products containing these chemicals can be harmful to dogs. Even small amounts can cause gastrointestinal distress, vomiting, and diarrhea.

  4. Carcinogenic Risk: The contamination of MIT and CMIT with formaldehyde and acetaldehyde raises concerns about the long-term carcinogenic risk in dogs. Chronic exposure to these contaminants is associated with an increased risk of cancer.

Alternatives to MIT and CMIT

To ensure the safety of your furry companion, it's crucial to choose pet grooming products that do not contain MIT or CMIT. Look for natural and hypoallergenic options, as well as products that are free of harsh chemicals and preservatives like 4-Legger

While MIT and CMIT are effective preservatives in personal care and pet grooming products, they come with significant risks, especially with long-term use.


These chemicals can cause skin irritation, allergies, toxicity, and may even pose a carcinogenic risk due to contamination with formaldehyde and acetaldehyde. To ensure the safety and well-being of your beloved pet, always read product labels carefully, and opt for pet care products that use safer, natural alternatives.