Why Does My Scalp Itch After I Wash My Hair?
Itching of the scalp after washing hair is a common issue we treat in the clinic. This blog post will discuss why this happens and how we can treat this problem both through changes to the hair washing routine and prescription strength products offered through Allura Medicinals.
At the most basic level, itching is caused by the activation of nerves inside the skin. This can happen for many reasons, but in any form of dermatitis (such as seborrheic dermatitis, also known as dandruff) the cause tends to be a weakened skin barrier that can no longer perform its basic functions.
The skin barrier is a layer on the very top of our skin composed of proteins and lipids that are woven together into a tight meshwork. When this barrier is working properly it performs two essential functions. First, it keeps water inside of your skin, which then leads to the feel of soft, hydrated, healthy skin. Second, the skin barrier will repel things like irritating substances (soaps, detergents, etc), allergens, bacteria, and yeast.
Several things can lead to a breakdown in our skin’s barrier, and thus the loss of the functioning of the barrier which then leads to itching, dryness, and flaking of the scalp. Some people simply, for genetic reasons, do not build as robust of a skin barrier as others. These people often know they have “sensitive skin” but may not realize why this is the case. Extreme examples of this are in patients with chronic eczema.
The other, more common reason, for a broken down skin barrier is over use of soaps, detergents, and shampoos. These products are all designed to break down proteins and lipids, which is exactly what the skin barrier is made of! Even the “sensitive skin” products will still cause some disruption to the barrier.
As mentioned above, the skin barrier is there to repel irritating substances away from the skin. If this barrier is compromised then anything we put on our skin will penetrate far deeper into the skin than it should to exactly where the itch nerves live in our skin. So when someone with an impaired skin barrier, often due to seborrheic dermatitis (dandruff), washes their hair the shampoo and conditioner activate these nerves and cause the itching. The hot water contacting the scalp temporarily suppresses the itch nerves, so the itching tends to get worse right after the shower is over. The answer to this problem is repairing the skin barrier; if we can do that then these substances will no longer irritate the skin and cause itching.
In patients with seborrheic dermatitis (dandruff) and scalp psoriasis, the best way to repair the skin barrier is to address the underlying medical condition. As we discuss in another blog post we do that through the combined use of medications that suppress yeast growth and also suppress the skin’s inflammatory reaction to the yeast. Once the barrier is repaired the itching will stop and then we maintain the response with continued use of these products. However, as mentioned above, too much use of any shampoo will further degrade the skin barrier, therefore we recommend the use of our shampoo 2-3 times a week only, allowing it to sit in the scalp for 5 minutes for maximum activation of the medications.