Missouri Barber Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

The most common cause of allergic reactions to hair color is paraphenylenediamine (PPD). PPD is a chemical commonly used in many permanent hair dyes and is known for its ability to provide rich and lasting color. However, it is also a well-documented allergen. When applied to the hair or scalp, some individuals can develop an allergic reaction, which may manifest as redness, itching, swelling, or other dermatological issues.

While other components in hair dyes, such as ammonia and hydrogen peroxide, can cause irritation or allergic-like reactions, they are less frequently the direct source of allergic reactions compared to PPD. Alcohol can also serve as an irritant but typically does not lead to the same type of allergic responses associated with PPD exposure. Understanding the role of PPD is vital for both professionals and clients in the beauty industry, as proper patch testing and awareness can help prevent adverse reactions.