Hair Dye Allergy After SARS-COV-2 (COVID 19) Infection: What are we to Make of These Observations?

More Study is Needed To Understand the Significance of Observations.

New observations from hair salons are increasingly leading many to wonder if acquiring COVID 19 infection makes a person more likely to develop allergic reactions. The real answer is not known yet, but hopefully the press these stories generate will encourage proper study. We don’t have such proper studies - yet.

COVID 19 and Hair Dyes: Not A New Story

I saw today a flurry of stories covering the issue. The reality is that the possible relationship between prior COVID 19 and susceptibility to allergic hair dye reactions first popped up in the UK over a year ago.

The story caught my attention in 2020 and I’ve been following it since. Not because I can exactly prove there is any relationship quite yet, but because the story needs more exploration.

Hair dye use is common - and only getting more common. In fact, a vast majority of women have used hair dyes in the past year. Data that follows trends show that over the past 20 years five important trends have also emerged: 1) more high school students are getting their hair dyed, 2) more women in their 20s are getting their hair dyed 3) more men in their 20s are getting their hair dyed and 4) people are getting their hair dyed more frequently with less time between dyeing and 5) children are now having reactions to PPD. The median age to get hair dyed is now in the teenage years. Hair dye use is no longer solely for greying.

For over 100 years, PPD has been the main agent in hair dyes. Although PPD itself was first made in 1833, it became a part of dyes that we know today back in around 1893. It’s a fantastic dye and gives amazingly consistent color results. That’s why the cosmetics industry loves it. It has low molecular weight, can penetrate the hair shaft easily and gives good color.

It’s been known for many years that PPD can give all sorts of skin reactions. Various regulatory agencies have limited concentrations of PPD in hair dyes over the years. Some counties have even pulled PPD containing hair dyes from the market for a few years before returning them back to the shelves with stricter regulations. Some countries ban PPD in leave on products, but have not regulated concentrations in wash away products as much.

Consumers and hair industry is increasingly aware of PPD related reactions. The challenge is that PPD has so many different names. One needs to be on the lookout for names such as p-phenylenediamine, para-phenylenediamine, 4-aminoaniline; 1,4-benzenediamine; p-diaminobenzene; 1,4-diaminobenzene; 1,4-phenylene diamine

Allergic Contact Dermatitis (ACD): The Medical Term for the Allergy that Happens from Hair Dyes

The type of allergy that is being discussed here is called allergic contact dermatitis or “ACD.” It’s the same type of allergic reaction that happens when one gets a rash on the leg or arm after hiking in the forest that contains poison ivy or poison oak. The allergen touches the skin, gets absorbed through the skin and then the immune system mounts a response. The first few exposures simply wake up the immune system and don’t typically lead to any problems. Further exposures over time are what lead to the hair dye reactions that get attention.

When a person gets their hair dyed, PPD will get into the blood within 2 hours.

What does hair dye allergy look like? What might a person experience?

Hair dye allergy is quite varied. Surpringly, one of the most common areas affected is the face. The scalp is second place and neck is third. Some individuals with hair dye allergy develop redness on the scalp, itching, prickling, burning, scale. Some develop oozing and fever and feel unwell.

Some reactions are much more extensive than just the scalp. Some with ACD to hair dye develop eyelid swelling and some develop swelling in the throat or airways. Some develop true anaphylaxis - which is a true medical emergency requiring lifesaving intervention.

How common is hair dye allergy? Who gets it?

Not everyone who uses a hair dye will get allergic contact dermatitis to the dye. In fact, the number is probably under 1 % in the entire population. In patients that set foot in a dermatology clinic to discuss potential allergies, the number is much higher at 2-6 %. Many people will use hair dyes through their life without any trouble at all. People who get their hair dyed more often raise their risk a bit, and so do hairdressers who deal with dyes often. Individuals from certain counties may also have different risks. Women are more likely to have hair dye allergies than men.

The Chemicals Causing Hair Dye AC

There are many chemicals in hair dyes that have the potential to cause ACD. The most common of these is “PPD” or paraphenylenediamine. But PPD is only one of the allergens. The others include para toluene diamine or “PTD” and amino phenol and others.

Testing For ACD: Patch Testing

Patch testing is a test to determine confidently if a patient is truly allergic to a chemical or not. It is a test that is done typically in a dermatologist’s office. Pure chemicals are placed on the patient’s back and covered. The so called “patches” are left in place for 48 hours. The patches are then removed and the dermatologist proceeds to observe what happens to the underlying skin over the next 24-72 hours. Skin that stays red or gets even more red, is said to have experienced an allergic contact dermatitis from the chemical that overlying the area. Skin that becomes less red and returns quickly to normal is said to have had an irritant contact dermatitis.

For PPD, 0.3 to 1 % PPD in petrolatum is typically the concentration that gets patch tested.

Patch testing is a standardized method for determine if a patient is truly allergic to a chemical or not.

Conclusions

Hair dye allergy is an important subject. Hair dye allergies can be life threatening so we need to take any new information really seriously. It if turns out it’s true, we need to act and change the way we do things to ensure public safety. If it turns out it’s false, we carry on.

There is a thought amongst many that prior COVID 19 infection increases the risk of hair dye allergy. Whether it’s true or not and to what magnitude a person’s risk is increased is not known yet. More studies are urgently needed.

The type of study that is needed is simple: Patients with prior COVID 19 infection need to be patch tested for allergies. One can then carefully evaluate if the positivity rate to PPD and other hair dyes is truly increased above the general population rate or not. Data can be compared to individuals without COVID 19 infection.

For now, we need to heed the advice of hair dye manufactures: all hair dyes should be patch tested behind the ear before use. If one changes color, it should be tested again. One needs to have a low threshold for suspecting ACD under any circumstance following hair dye but for now we need to have a low threshold post COVID to suspected ACD if there are unusual or prolonged inflammatory reactions.

If hair dye allergy is suspected, one needs to consider using PPD free dyes or other dyes. Most hair salons are well versed in ordering PPD free dyes for their customers. Involvement of an experienced dermatologist is helpful.