What causes an itchy scalp?

An itchy scalp, also sometimes known as scalp pruritus, can cause irritating and uncomfortable symptoms, including a strong desire to scratch the scalp frequently. Having an itchy scalp alone isn’t usually something you need to be worried about, although it can be incredibly frustrating for sufferers and may indicate another underlying condition. In this post we explain the science behind what causes an itch and look at some of the most common itchy scalp causes.


The science of an itchy scalp

An itch is simply your body’s response when it suffers some form of skin irritation. This irritation can be triggered outside the body, such as when a plant rubs against your skin, or from something that has happened inside your body to cause the itch, such as an allergic reaction or skin condition like psoriasis.

When your brain detects an irritation, signals are sent to that location in an instant, causing you to scratch. The reason scratching an itch feels good is that it actually triggers tiny pain signals, which form a distraction from the irritation. In some cases, the pain-fighting chemical serotonin can be released, which may cause the area to feel even more itchy and increase the temptation to scratch. This can be a vicious cycle, leading to further irritation, which in turn leads to more itching, and so on. The scalp is one of the areas of the body most prone to becoming itchy.


Common causes of an itchy scalp

There are a number of reasons your scalp might itch and we have outlined some of these causes below.



The most common cause of an itchy scalp is dandruff, a mild form of the condition known as seborrhoeic dermatitis (see below). Dandruff causes white or grey flakes to appear on the scalp and in the hair and people with the condition may find that their scalp is itchy too. The primary cause is natural yeast called Malassezia, to which some people are especially sensitive.

Seborrhoeic dermatitis

This condition is considered to be a chronic form of eczema. The exact cause is unknown, but it is thought to be triggered by an overgrowth or overreaction to the Malassezia fungus. Hormonal and environmental changes can also contribute to the condition, which results in greasy, swollen and flaking skin, leading to an itchy scalp.

Contact dermatitis

This is another form of eczema which causes the skin to become dry and irritated. Contact dermatitis is caused when an irritant or allergen, like a detergent or a cosmetic ingredient, comes into contact with the skin and causes an adverse reaction. This reaction can cause rashes on the scalp, making the area dry and irritated.


Psoriasis is a chronic skin condition which causes red, crusty patches of skin, often covered in silvery scales. It is a result of skin cells being reproduced too quickly (within a week as opposed to the more usual timescale of a month). This results in a buildup of skin cells, with the buildup being what causes the scalp to itch.

If you have an itchy scalp, a therapeutic shampoo, such as Polytar Scalp Shampoo with 4% Coal Tar, may help to provide relief. Coal tar has anti-itch, anti-inflammatory and antibacterial properties which work to soothe itching. It’s important to be aware that psoriasis and eczema are medical conditions, so speaking to a healthcare professional will help you to understand the most suitable treatment for your condition.