Conditions of the scalp
Many skin conditions that affect the rest of the body also affect the scalp and cause itching, redness, scaling and crusting of the skin of the scalp. These include
- inflammatory skin conditions, like dermatitis and eczema
- seborrhoeic dermatitis
Dermatitis is a general term that applies to inflammation of the skin and can occur affect any area of the skin, including the scalp. There are many possible causes for dermatitis such as an allergic reaction, contact with an irritant or excessively dry skin. Eczema, another term for dermatitis usually refers to chronic itchy inflammatory skin condition that is also known as atopic eczema or atopic dermatitis, as there is a genetic predisposition due to an inherited atopic tendency, with a family history of three closely linked conditions: asthma, eczema and hay fever.
Seborrhoeic dermatitis is a chronic form of dermatitis that affects the scalp and is thought to be due to an inflammatory reaction to a common inhabitant of the skin, the yeast fungus Malassezia (previously called Pityrosporum) that lives in the sebum. Symptoms include greasy scaling of the scalp with itchy red and crusty patches and flaky persistent dandruff, which is a common mild form of seborrhoeic dermatitis, characterised by flaking of the skin on the scalp.
Psoriasis a non-allergic, chronic autoimmune skin condition that has a genetic predisposition, where certain cells of the immune system overproduce inflammatory chemicals that stimulate excessive growth and proliferation of keratinocytes (epidermal skin cells), causing thickening and scaling of the skin as well as inflammation.
Treatments for scalp conditions
Medications used to treat inflammatory skin conditions of the scalp contain a range of ingredients that work by different mechanisms of action.
- Clobetasol and fluocinolone are potent synthetic corticosteroid hormones with anti-inflammatory action based on blocking the production of chemicals that are inflammatory mediators, particularly prostaglandins and leukotrienes. This action prevents migration of inflammatory cells, which helps dampen down the inflammatory response; reducing capillary wall permeability and promoting vasoconstriction, which causes blood vessel narrowing, and helps reduce swelling and redness.
- Ketonazole is an antifungal that kills the yeast fungus Malassezia responsible for seborrhoeic dermatitis, by inhibiting the synthesis of ergosterol, an important component of fungal cell membrane that weakens the membrane and kills the fungus. Zinc pyrithione is a chemical antifungal that is sometimes used in combination with ketonazole to enhance its antifungal action.
- Salicylic acid is a keratolytic that is included in treatments for hyperkeratotic conditions, which are scaly skin conditions where the skin has become thickened, scaly and flaky. It works by softening keratin, which is a fibrous structural protein found in the upper layer of the skin, and this helps loosen the dry scaly skin and also allows other medications like corticosteroids to penetrate the skin more easily.
- Coal tar is also used for hyperkeratotic conditions to reduce scaling itching and inflammation, due to its antimicrobial and antipruritic (reduces itching) properties. It is also a keratoplastic and interacts with skin cells to slow down the rapid growth of keratinocytes to normal turnover so that dead cells are shed from the surface, which reduces scaling.
- Calcipotroil is used as a topical treatment for psoriasis and helps to prevent over production of hardened keratinocytes, restores normal cell growth and behaviour to the epidermal skin cells, as well as reducing inflammation. Calcipotroil, a derivative of calcitriol or Vitamin D works by regulating cell growth and differentiation and modulating the immune system, causing inhibition of cell proliferation and stimulation of cell differentiation. This action helps reduce the scaling and thickening of psoriatic plaques and relieves symptoms of psoriasis.