Itchy Hyperpigmented Lesions: Diagnosis & Advice

(i) Most Likely Diagnosis

The most likely diagnosis is allergic contact dermatitis (ACD) secondary to paraphenylenediamine (PPD) or other chemicals present in the hair dye. PPD is a common allergen found in permanent hair dyes, and its use is strongly associated with ACD, particularly on the scalp, face, and ears. The temporal relationship – the onset of symptoms five months after starting hair dye use – strongly supports this diagnosis. The lesions being itchy, hyperpigmented, and scaly are also consistent with chronic ACD.

(ii) How to Confirm the Diagnosis

Confirmation of the diagnosis requires further investigation:

• Patch Testing: This is the gold standard for diagnosing ACD. A standardized series of allergens, including PPD, are applied to the patient’s back under occlusive patches for 48 hours. Readings are taken at 48, 72, and 96 hours to assess for a positive reaction (erythema, edema, vesicles).
• Detailed History: A thorough history should be taken, including a complete list of products used (hair dye brand, color), frequency of use, and any other potential allergens.
• Skin Biopsy (Optional): While not always necessary, a skin biopsy can help rule out other conditions mimicking ACD, such as eczema or psoriasis. Histopathology may show spongiosis, epidermal hyperplasia, and a mixed inflammatory infiltrate.
• Repeat Open Application Test (ROAT): In cases where patch testing is inconclusive, a ROAT can be performed. A small amount of the suspected allergen (hair dye) is applied to a small area of skin for a limited period, and the site is monitored for a reaction.

(iii) Medical Advice

The following medical advice should be given to the lady:

• Strict Avoidance: The most important step is to immediately discontinue the use of the hair dye. She should also avoid other products containing PPD or similar chemicals. Reading ingredient lists carefully is crucial.
• Symptomatic Treatment:
  • Topical Corticosteroids: Moderate- to high-potency topical corticosteroids (e.g., betamethasone dipropionate) can be used to reduce inflammation and itching. The potency should be adjusted based on the severity of the dermatitis and the location of the lesions.
  • Emollients: Regular use of emollients (e.g., petrolatum, ceramide-containing creams) helps restore the skin barrier and reduce dryness.
  • Antihistamines: Oral antihistamines (e.g., cetirizine, loratadine) can help relieve itching, especially at night.
• Alternative Hair Dye Options: Discuss alternative hair coloring options with the patient.
  • Semi-permanent dyes: These generally contain lower concentrations of PPD or may not contain it at all.
  • Vegetable-based dyes: Henna and other vegetable dyes are less likely to cause ACD, but allergic reactions can still occur.
• Education: Educate the patient about ACD, its causes, and how to prevent future episodes.
• Follow-up: Schedule a follow-up appointment to assess the response to treatment and discuss further management options if needed.