Tea tree oil has become one of the most common ingredients to find in skin care products. It is known for its antimicrobial and antiseptic properties in it’s activity against bacteria, viruses, fungus, mites, etc. When added to scalp exfoliators it is likely addressing some of the underlying triggers for scalp inflammation that result in scaling and itching.
The only caution is that it does have about a 1-2% chance of causing a contact dermatitis in those that use it. If using a product that has tea tree oil and your itching and flaking is getting worse, it’s important to take a look at your products and make sure they are not making it worse!