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  • Scalp contact dermatitis (SCD) is an inflammatory disorder of the scalp triggered by the application of one or more allergenic substances able to evoke either an irritant or immune response.

  • The burden of SCD is increasing worldwide due to the growing trend of performing cosmetic procedures on the scalp, which includes hair dyes, bleaches, extensions, wigs, perming, and straightening.

  • Keratin treatments are a common cause of scalp dermatitis.


  • The signs of SCD often extend to surrounding or distant anatomical areas, where the clinical signs often appear more pronounced than on the scalp.

  • Itching and burning are almost constant symptoms of SCD and should always trigger suspicion of possible sensitization.


  • Treatment of acute SCD consists of topical or systemic corticosteroids according to the severity of the delayed-type reaction.

  • Immediate-type reactions, including contact urticaria, benefit from antihistamine therapy and systemic steroids.

  • Long-term treatment relies on allergen avoidance.

  • Dupilumab can be considered in severe cases.


  • Delayed-type reactions always require a primary sensitization. This event may occur after exposure to the same allergen coming from a different source than the offending one; however, can also be secondary to long-term use of any topical product.

  • Always assess the clinical relevance of positive patch tests and consider allergen cross-reactivity.


  • The latency between a SCD and the initial use of a scalp product could last a long time.

  • Topical minoxidil causes much more frequently skin irritation than a skin allergy.

  • Individuals with atopic diathesis are at increased risk of developing immediate-type reactions to allergens, including contact urticaria or respiratory symptoms.


  • Shampoos are a very uncommon cause of contact dermatitis as they are diluted and contact with the skin is short.

  • A mild to severe hair loss may begin 2 to 4 months after the episode of SCD.

  • Aggravation of androgenetic alopecia is a possible complication of SCD.


  • Do not overlook scalp symptoms or treatment failure and aggravation of the underlying scalp disorders; these can be key signs of an allergic reaction to the applied products.

  • In the case of a suspected or confirmed allergy to metals, pay maximum attention to the use of hair accessories, hairpins, glasses, and jewelry in nearby body areas.

  • Para-phenylenediamine (PPD) is the most common allergen responsible for SCD due to hair dyes.

  • Allergic hair dye patients willing to use a new dye should have a “repeated open application test” and wait at least 48 hours for a possible allergic reaction.

  • Alternative hair dyes for sensitized patients include botanical dyes, such as Henna, Cassia, and Indigo, and some PPD derivatives with a lower skin sensitization potential than PPD, such as para-toluenediamine sulfate, 4-amino-2-hydroxytoluene, and 2-methoxymethyl-p-phenylenediamine.


SCD represents an important inflammatory disease that mainly afflicts women over the age of 40. ...

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