Which ingredient should be avoided if a client has a known allergy during hair treatment?

Ammonia is a chemical that is commonly used in various hair treatments, particularly in hair coloring and perm solutions due to its ability to open the hair cuticle for better penetration of other ingredients. However, it can cause significant irritation, especially to clients with sensitive skin or allergies. If a client has a known allergy to ammonia, using products containing this ingredient can trigger severe allergic reactions, ranging from mild skin irritations to more severe respiratory issues.

In a salon setting, it is crucial to ensure the safety and comfort of clients by avoiding known allergens. While other ingredients listed, such as hydrogen peroxide, carbomer, and fragrance, may also cause reactions in certain individuals, ammonia is particularly notorious for its strong alkaline nature and potential for causing irritation, making it essential to avoid in clients known to be allergic to it. Thus, ensuring that ammonia is excluded from treatments for allergic clients is a vital practice in cosmetology.