Flaking Scalp, Silvery Plaques and a Colour Booked Today
Aoife, 41, is booked for a global colour (5/0 with 6% on 50% grey) and a scalp treatment. Her consultation form shows a patch test done three days ago with no reaction and a colour ten weeks ago with no problems. On examination she reports itching that is worse at night, and you see greasy yellow scale along the hairline, in the eyebrows and behind the ears. At the nape there are two well-defined red plaques with silvery scale; one is excoriated and slightly moist where she has scratched, with a trace of blood on the comb. She has used a pharmacy ketoconazole 2% shampoo for two weeks and thinks it has helped a little. She takes no other medication and has no known allergies. Her scalp is tender when you part the hair. She is going on holiday in five days and wants the colour done today.
1. What conditions are you considering, and which finding is the red flag?
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The picture has two components, and the second one is the red flag.
Greasy yellow scale along the hairline, in the eyebrows and behind the ears, with itching worse at night, most closely matches seborrhoeic dermatitis - a Malassezia-related inflammatory condition of sebum-rich areas. Ketoconazole 2% is the right product, but two weeks is often not long enough and partial improvement is expected at this stage.
The two well-demarcated plaques with silvery scale at the nape could be psoriasis. Plaques with silvery scale that bleed when the scale is lifted (Auspitz sign), often occipital and behind the ears, are characteristic. Psoriasis is not infectious, but it is a medical condition, and plaques are made worse by trauma - including scratching and chemical irritation.
The excoriated, moist plaque with blood on the comb is the red flag. Moist, weeping, broken skin may be secondarily infected, with bacteria entering through scratch breaks. That needs referral, not a salon treatment.
Less likely but worth ruling out: tinea capitis (usually children, with patchy hair loss and broken hairs), contact dermatitis (would follow a product rather than this distribution), and lichen planus. Action: do not colour today, and refer to the pharmacist or GP with a factual description of what you saw.
2. A negative patch test was recorded three days ago. Does that authorise you to colour today?
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No. A negative patch test tells you only that the skin it was applied to did not react to that product 48 hours later. It does not tell you that broken, inflamed skin will tolerate a tint, and it does not protect you if the reaction that follows comes from applying colour to a compromised scalp.
Mechanically: inflamed or excoriated skin has a reduced barrier, so the dye and the alkaline agent are absorbed more readily. That means more stinging and burning, and a higher chance of a sensitisation reaction to PPD or to the alkaliser. Sensitisation is permanent - once it happens she can no longer be coloured with oxidative dyes at all. There is also an infection risk: tint occluded under a cap on broken skin is a good environment for bacteria.
Psoriasis adds a further reason for caution, since plaques can be triggered or spread by irritation.
So the patch test is valid for what it was, but the skin condition overrides it. Postpone the colour until the scalp has healed and reassess. When she returns, repeat the patch test 48 hours beforehand, because a sensitisation event in the meantime would change the result.
3. What can you offer her today, what advice and referral do you give, and what do you record?
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Today: a dry scalp consultation and a gentle service that avoids broken skin. No colour, no exfoliating scrub, and no essential-oil-heavy massage over the plaques. You can shampoo with a mild, fragrance-free shampoo, condition mid-lengths and ends, and dry without tension, keeping product off the excoriated area.
Advice, in plain language:
- Continue the ketoconazole shampoo as directed by the pharmacist, usually twice weekly, left on for 3-5 minutes before rinsing.
- Do not scratch; if the itch is severe, ask the pharmacist about an antihistamine or a mild topical preparation.
- Avoid tight hats, harsh shampoos and picking the scale; change pillowcases regularly.
- See the GP if the plaques spread, weep, or the hair starts thinning in patches.
Reschedule the colour for two to three weeks, once the skin has settled, with a repeat patch test 48 hours before and a formula that gives grey coverage without unnecessary extras.
Record: the condition as observed (not a diagnosis), the reason the colour was declined, the referral made, the advice given, the rebooking, and her agreement. If the condition recurs, that record supports the same decision next time and shows you acted consistently.