We all experience itching of the scalp every now and then. This is usually not serious. In most cases it is just temporary scalp irritation but when it is ongoing and accompanied by a rash or loss of hair then it needs to be investigated further. Even when there is no significant scalp problem, excessive scratching can damage the skin and lead to other conditions, like scalp infections.
Why does the scalp itch?
The scalp is the skin that overlies the top of the head and is rich in hair follicles and oil glands. It is covered by scalp hair in most people, which may be of varying lengths depending on individual factors. Like skin anywhere else on the body, the scalp may be prone to irritation, damage and diseases which can lead to itching. It is important to note that an itchy scalp is a symptom and not a separate disease.
Itching usually indicates that there is some irritation or damage to the skin. Specialized itch receptors in the skin sends signals back to the brain which we perceive as an itchy sensation. This prompts us to scratch the area in order to relieve the itching. The itch and scratch reponse is the body’s mechanism to remove any irritation from the skin surface before it causes damage, like a crawling insect may trigger an itchy sensation and scratching removes it. However, when itching is ongoing and accompanied by a rash or other symptoms then it needs to be treated.
Causes of Itchy Scalp
There are a number of different causes of an itchy scalp. It is not always due to a specific disease. Sometimes temporary environmental factors may trigger itching. Transient itching of the scalp occurs in most people on a daily basis. Scratching of the scalp can also be a social signal, indicating confusion, nervousness or thinking. In these cases there is usually no itching of the scalp.
Sweating is a normal mechanism to cool down the surface of a part of the body. It is more likely to occur during hot weather, especially when an area of the body is covered for prolonged periods of time. People who cover their head with hats and scarves are more likely to experience scalp sweating. The sweat acts as an irritant as it is unable to evaporate from the skin surface.
Infrequent washing of the hair and scalp causesa build up of dust, dead skin cells, sweat, oils and microbes. This can irritate the skin and therefore lead to itching. However, excessive washing of the hair may also irritate the skin as it dries the scalp surface. This may further be exacerbated when using shampoos or conditions with harsh substances that irritate the scalp.
Dry skin is one of the most common causes of itching anywhere in the body, and the same applies to the scalp. Despite the large amount of oil glands on the scalp surface, drying may occur for various reasons such as damage of the scalp, excessive washing, the use of harsh chemicals on the scalp surface and environmental factors. Dry skin is also prone to various skin diseases such as fungal and bacterial infections of the scalp.
Hair care and styling involves a host of activities that utilises chemicals for washing, bleaching, colouring and styling the hair. This ranges from shampoos and conditioners to hair dyes and styling gels. The ingredients within these products can be harsh and irritate the scalp. Some people have an allergy to certain ingredients which may be triggered by exposure. For example PPD (paraphenylenediamine) found in permanent hair dyes can be an allergen.
Apart from chemical injury to the scalp, mechanical and electormagnetic injury may also be a cause of an itchy scalp. Mechanical injury may occur with scratching the scalp vigorously or with the use of hard and/or sharp objects on the scalp. Another possibility is electromagnetic injury caused by sun exposure which is known as sunburn.
The scalp can become infected, mainly due to a fungal or bacteria infection. Fungal infections of the scalp are usually caused by dermatophytes, which are a type of fungus. These infections are also commonly referred to as scalp ringworm or it is known by the medical term tinea capitis. A fungus is not a worm.
Bacterial infections more often involve the follicles of the scalp as is the case with folliculitis. However, superficial bacterial infections such as impetigo may also occur especially if a wound on the scalp becomes infected. Other infections, such as chickenpox which is due to a virus, may also cause lesions on the head.
The main parasite that infests the human scalp is head lice. These wingless insects feed on human blood from the scalp and can cause significant itching. The head louse (Pediculus humanus) is different from the lice that can infest the body (body louse) or pubic region (pubic louse or “crabs”). Scabies, which is caused by a mite, can also cause an itchy scalp but the scalp is not a common site involved in this type of skin infestation.
A host of different skin diseases can affect the scalp. This includes conditions such as:
- Atopic dermatitis (eczema)
- Contact dermatitis (irritant or allergic)
- Seborrheic dermatitis
Treatment of Itchy Scalp
The treatment of an itchy scalp depends on the underlying cause. It is therefore important that a doctor examines the area and further consultation may be needed with a dermatologist or trichologist. While skin diseases usually require medical treatment with drugs such as antibiotics, antifungal agents, corticosteroids, salicylic acid, isotretinoin and so on, other common conditions that may cause an itchy scalp can be managed with simple lifestyle measures.
- Wash the hair and scalp regularly with an unscented soap or shampoo. Baby shampoo is mild and usually does not cause irritation of the scalp or trigger allergic reactions.
- Ensure that the hair is thoroughly rinsed of shampoo and any other hair care product.
- Minimize the use of an electric hair dryer or use it on a low heat setting for short periods.
- Do not brush or comb the hair vigorously or with force. Gentle brushing or combing will suffice.
- Head lice can be treated with over-the-counter applications in most cases. Thorough combing of the hair with a fine comb helps to remove the lice and nits (eggs) from the hair.
An itchy scalp is a symptom of some underlying problem. Always consult with a medical professional if these lifestyle measures do not relieve the itching or if there is any sign of a rash, discharge, blood and/or hair loss form the scalp.