Itchy scalp or scalp pruritus is a common complaint for which individuals seek a trichologist or a dermatologist consultation. Epidemiological studies conducted in France showed that more than 25% of the population are in fact subject to active scalp itching. There are numerous underlying causes for this condition, but the reason it is often associated with hair loss is because itchiness leads to aggressive scratching that then causes direct damage to hair follicles and affects hair growth. Therefore, a thorough clinical evaluation is always needed to diagnose the exact cause behind an itchy scalp, as multiple reasons behind its appearance are easily reversible with defined management protocols that can prevent further hair loss.
Common causes behind an itchy scalp
The clinical classification of scalp pruritus can be made according to potential underlying diseases, for instance:
- Inflammatory causes: such as seborrhoeic dermatitis, psoriasis, atopic dermatitis, contact dermatitis, sensitive scalp, lichen planopilaris, alopecia areata, urticaria, scars, insect bites, etc.
- Infectious causes: folliculitis, fungal, bacterial, viral infections, scabies, etc.
- Autoimmune causes: alopecia areata and dermatitis herpetiformis.
- Neoplasms: lymphoma, leukemic infiltrates of the skin.
- Environmental causes: Dust, dirt, and pollution can also accumulate and together cause itchiness of the scalp.
Some of the above mentioned common causes and their association with hair loss are briefly discussed below.
Folliculitis is the inflammation of the hair follicle that can cause both transient and permanent hair loss. It can be a result of an infectious agent such as bacteria (most commonly staphylococcus aureus), fungus, or viruses. Folliculitis occurs when the hair follicles are exposed to these pathogens, for example, after an insect bite, shaving, braiding too close to the scalp or scratching the scalp frequently. These inflammatory conditions cause severe itching and rashes that heal with crusting. Fortunately, folliculitis can be efficiently managed with oral and topical, anti-bacterial, and anti-fungal medications.
Seborrheic dermatitis is a chronic skin disorder that causes red, itchy, scaly skin, and is estimated to be prevalent among 3-5% of the world’s population. As well as causing scalp itchiness the most common symptom of seborrheic dermatitis is visible dandruff that affects 15-20% of people.
The etiology of this disease remains unknown, however, multiple environmental, genetic, and immunological factors are thought to contribute to its pathogenesis. Colonization of fungal species Malassezia globosa (which targets the sebum-producing skin) is also a widely accepted cause of this condition. It is believed that this microbe breaks down the natural sebum, causing irritation and inflammation of hair follicles. The itching associated with the condition also increases the frequency of scalp scratching, directly damaging the hair follicle and consequently causing hair loss.
Seborrheic dermatitis can be successfully treated using anti-fungal agents such as ketoconazole and substances like coal tar, salicylic acid, and selenium sulfide.
Harsh Shampoos and Hair Products
Hair products such as shampoos, hair sprays, hair dyes, styling, and other scalp care products can frequently cause chemical injury or allergic reactions to the scalp. These present as an itchy scalp with varying degrees of hair loss. Even applying the harsh topical product for hair loss treatment can further exacerbate hair loss in sensitive scalps.
Sodium chloride, a common ingredient used as a thickener in shampoos, can also cause dry, itchy scalp that is vulnerable to hair loss. Another common cause of allergic scalp reaction is a chemical called paraphenylenediamine, which is a well-known component of many hair dyes.
The most practical solution to this form of hair loss is the discontinuation of the offending product and the use of a less irritating alternative. A nourishing shampoo that is also gentle on the scalp should be preferred over complex formulas to prevent such problems recurring in the future.
Scalp ringworm, also called the tinea capitis, is a fungal infection of the scalp and hair shafts that causes itchy, scaly, and bald patches on the head. This highly contagious infection is frequently common among toddlers and school-age children with around 50% of cases reported in children under 15 years of age. This type of fungus is known for invading the scalp skin and consuming keratin as its nutrient source. With a deficiency of keratin in the hair follicle, the infected hairs become brittle and eventually fall before their time. Fortunately, Tinea capitis can be effectively treated by oral antifungal griseofulvin, which has shown to have an 88-100% treatment success rate.
This is a permanent type of hair loss that occurs when a chronic autoimmune condition known as lichen planus affects hairy parts of the skin, causing scaly skin, and hair loss. Scalp itching is present in almost 70% of these patients.
This condition is associated with the destruction of hair follicles and their replacement with scar tissue, resulting in permanent hair loss. Lichen planopilaris is still considered an orphan disease as no definitive prevalence data or proven effective treatments have yet been found. However, many dermatologists believe that this condition spontaneously resolves itself over time and that the process may be enhanced by corticosteroid administration.
Another autoimmune condition that is associated with itchy scalp and patchy hair loss is Alopecia Areata. This universal condition affects every 1 in 1000 individuals and has an equal prevalence in both men and women. Here, the body’s own t-cell attacks the follicular antigen in genetically predisposed individuals. Therefore, immune therapies and steroids can be readily used to manage Alopecia Areata.
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