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Allergy Awareness Week: Patch Testing

Published date 22 April 2024

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Today marks the start of Allergy Awareness Week, and we are teaming up with Colourstart to raise awareness around the topic of patch testing, and why this is a crucial step when taking on new clients. Let's take a deep dive into the importance of patch testing alongside the allergy experts at Colourstart, and why it is so important to raise awareness of patch testing throughout the industry.

Hair colour allergies are a concern for any colourist, and skin testing is essential to ensure your client doesn't have a reaction. Currently, there are three ways of testing that the leading industry bodies have recognised, and one which is Colourstart. This is the first clinically proven test for allergy to hair colour to be licensed by the Medicines and Healthcare products Regulatory Agency (MHRA). Why do we love it? Well, it's universal and test against PPD, which means you can use it on all colour brands. Every. Single. One.

We've caught up with the allergy experts at Colourstart to get the lowdown on some of most frequently googled questions so you don't have to.

Q&A with the allergy experts at Colourstart

Does the body always react when it has an allergic reaction?

Yes. The first time the body is exposed to an allergen it will react to it, but you won't necessarily notice this happening. It is once the exposure is repeated that the memory is triggered and the body can think it us under attack, going into protective mode and overreacts - hence symptoms appear. Each time you re-expose yourself this reaction can get worse. So, early diagnosis and avoidance are necessary.

Isn't an allergic reaction just the body getting used to something?

Unfortunately, this is not the case. Your body doesn't suddenly get used to something that it reacts to. An allergic reaction occurs when the body's immune system mistakenly tries to fight an allergen that it thinks will cause harm. It over produces the types of cells and biological agents that it thinks will cause harm. It over-produces the types of cells and biological agents that would normally fight off anything harmful, and this is what we call an allergic reaction. 

If a reaction to hair colour doesn't happen straight away, does this mean you won't get a reaction at all? 

No. Reactions don't necessarily happen straight away. A Type IV hypersensitivity reaction can be delayed 4 days or more after exposure. This is because it is not caused by a rush of antibodies (just like with an instant reaction) but by certain types of body's own T cells. These take time to be activated and start the process of stimulating other cells to attack the allergen.

What's the difference between an allergic reaction and a skin irritation?

The symptoms are similar, but it's not the same and there are ways to tell the difference. Irritant Contact Dermatitis (ICD) in particular is common among hairdressers, however, this is not an allergic reaction. It can be caused by multiple triggers, such as repeated exposure to a substance, such as chemicals, detergent or water. The good news is that this should improve and even clear completely once you avoid the irritant. Let your skin barrier rebuild and then make sure you use gloves and emollients. 

Can a reaction happen at any time, even if a client has been having the same colour for years?

Yes. This is why it's important to have a Colourstart test and complete the screening questions each time you colour. The questions have been designed to catch any potential triggers, such as if a client has a black henna tattoo.

How can PPD in a black henna tattoo cause an allergy?

High levels of PPD can trigger a reaction at any time. If a client has had a black henna tattoo it's not advisable to colour the hair. The legal limit for PPD in hair colour is 2%, in some cases henna tattoos have been found to contain up to 50%. Their use will increase the risk of an allergic reaction when using hair colour because this has now exposed the client to a large amount of PPD.

Why is frequent blob testing with colour that has PPD a concern?

The blob test has no control and is often repeated frequently, it is possible that this too can increase the risk of causing allergy to hair colour. This is why professional testing such as Colourstart is a great solution because it controls how you screen for allergy to hair colour with measured levels of PPD that are a fraction of the levels found in unmeasured blob tests.

If a hair colour doesn't contain PPD, can I have an allergic reaction?

If a client has an allergy to PPD then you should not use any oxidative hair colour, even if it claims to be PPD free. How would you know if a colour is an oxidative colour? If it requires a test before use, this normally an oxidative type of colour.

If I am allergic to PPD can I still have colour that doesn't touch my roots?

It's not recommended that you use any form of hair colour if you have an allergy to it.

Can chemicals such as PTD and ME+ cause an allergic reaction?

These are newer chemicals than PPD and they are thought to be less likely to cause sensitisation, but there is no evidence that new chemicals that replace PPD are less likely to cause an allergic reaction (elicitation). However, chemicals like ME+ (methoxymethyl para-phenylenediamine) that are used in permanent hair colourants claim to be less likely to make someone allergic to hair colour. Whatever colourant formula is used; it is really important to limit all exposure to these chemicals. Wearing good gloves is essential, as is controlling how much colour goes on a client's skin. That includes how frequently you test them, as over-exposure to PPD will have an adverse effect too.

If a client has an allergy to PPD are they likely to experience an allergy to PTD or ME+ or another oxidative hair colour?

Yes. These chemicals are so similar from an allergy perspective that they are said to 'cross-react'. PPD is overwhelmingly the most important chemical allergen in hair dye. Think about someone with a nut allergy. They don't avoid one particular nut - they avoid all nuts. It is the same with PPD. The chemistry with other chemicals is very similar and can cross-react to some degree, so you are taking a risk, even if it says PPD-free. They're all based on PTD and you have a chance of reacting. 

To safeguard against reactions, discover the Colourstart patch test, which will ensure you professionalise your allergy testing and protect your clients.

Shop Colourstart in selected Alan Howard stores or online.



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