Research was published in Contact Dermatitis looking at the instructions hair dye manufacturers give consumers about performing an allergy self-test before coloring their hair. It was a follow-on from a 2011 study, which found great variability in the instructions given, and whose authors expressed concern about the safety and reliability of the methods recommended.
The researchers looked at 40 oxidative hair dyes: the type using the highly allergenic ingredients PPD (para-phenylenediamine), PTD (para-toluenediamine) or related chemicals. Self-testing was recommended by all except one of the dyes. However, to quote the researchers:
The procedures varied greatly regarding the method of application, the amount of hair dye applied, the location and size of the application area, the number of applications, whether or not rinsing was performed after application, the reading times, and how a positive reaction was defined.
Researchers concluded this variation remains a worry.
What about alternative and ‘natural’ options?
If you avoid PPD / PTD and similar ingredients, alternative forms of hair dyes — covered extensively in this article — are less likely to trigger an allergy, but that doesn’t mean you shouldn’t still test them.
The innovative American-based brand Hairprint is a particularly interesting and unique concept. It is formulated to restore greying hair to its original black, or light, medium or dark brown state. Instead of PPD, it uses peroxide to oxidise plant and mineral ingredients to replicate original color in the hair shaft. Free patch test kits can be ordered from the Hairprint website (you only pay shipping / postage charges). They advise customers to mix the powder and liquid samples, and apply a small amount to your arm for 24 hours, before washing off, then waiting another 24 hours to check for a reaction. Hairprint also say that they have never had a confirmed allergic reaction to their product reported to them.
But other products vary. Pure botanical, mainly henna products are less likely to trigger allergies, so it’s perhaps to be expected that brands marketing them might advise a less stringent sensitivity test. Light Mountain Natural Color, who produce complete henna dye kits in beautifully designed boxes, advise a 24-hour sensitivity test: applying a small amount of dye mixture to the inner elbow, allow to dry, examine test area for signs of a reaction, rinse after 4 hours, examine again, and then examine again after a further 20 hours. Redness, burning, itching or swelling or any other ‘abnormal reactions’ mean you should not use the product.
Although with many of the kits you can open the products, remove some of the contents to conduct the patch test, and reseal them before you come to use them again once you’ve safely confirmed you are not allergic, like Hairprint, some responsible brands do offer ‘tester samples’.
Suvarna, who stock a huge range of 100% natural hair dyes for UK consumers, offer small samples of their It’s Pure Organics herbal hair colours, available for just £1.25, for example.
So what are consumers to do?
Dermatologists have been highlighting the limitations of hair dye self-tests for many years — but no real ‘revolution’ in advice or practice seems forthcoming.
Their concern is understandable: non-standard instructions are likely to popularise the idea that allergy test warnings are just a back-covering exercise by manufacturers to protect themselves.
Furthermore, there is the ongoing concern is that a test itself could sensitise the consumer to an allergen, and bring on an allergy that might not ordinarily develop. Other issues — mentioned in this 2012 paper — are that the skin is analysed by consumers not dermatologists, and that the tests have not been validated according to correct scientific criteria.
While the issues continue to be debated, the recommendation can only be to continue to perform allergy tests prior to any attempted colouring of your hair — be it at home or at a salon — according to packet instructions. They are vital — no matter whether or not you have a cosmetic allergy nor how ‘hypoallergenic’ the product you’re using may claim to be.
PPD-free (and PTD-free) options are likelier to be more ‘allergy friendly’, but remember that preservatives (such as methylisothiazolinone) can trigger allergies, and fragrances — often used to disguise odours in hair dyes — can be allergenic too.
The natural, mainly henna focused products listed in Category 1 here, are likely to be the safest for those with allergy — but the ‘price’ paid is that these are generally the least effective, non-permanent, and only last a few washes, with results mixed in quality.
And finally, remember if you have ever had a black henna tattoo — which likely contained PPD — then never attempt to test or use a PPD-containing permanent hair dye — ever!