People dye their hair to achieve all sorts of effects, from pastel purple streaks to buttery blonde strands to gray-concealing brunette tones to raven-sheen Goth. But there’s one look nobody wants — the scalp-reddening, eye-swelling and face-blistering effect of a hair-dye reaction. If you’re among the 5 percent of people allergic to hair dye, here’s what you need to know.

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Allergic reactions to hair dye rarely appear the first time you color your hair. Instead, they show up the second, third or fourth time around, says Dr. Zoe Diana Draelos, a clinical and research dermatologist and consulting professor of dermatology at Duke University. “You have to develop antibodies to the dye,” she says. “And that doesn’t happen until after the first exposure.”

Hair-dye allergies can happen to men or women at any age. “It used to be we saw it a lot more in older women, because they were the ones who dyed their hair to cover gray, as opposed to younger women who are now doing a lot more dyeing just for style and fashion purposes,” says Draelos, who practices at Dermatology Consulting Services in High Point, North Carolina. “Your immune system is better when you’re younger, so it’s possible younger individuals might get a more dramatic reaction.”

True hair-dye reactions can be quite vivid in the patients Draelos sees. “Their eyes are swollen shut,” she says. “Their faces are all puffy. They have lots of [fluid] in their faces. They may have blisters. The skin may be very tight and uncomfortable because there’s so much fluid.” Conjure up an image of someone with mosquito bites over his or her entire face, she says, and you have a sense of how a reaction to artificial hair color can appear.

Worse: “It can put you in the hospital,” Draelos says. “You can get an anaphylactic reaction.” There’s a reason the government requires warnings on the packages of hair-dye products. Labels must include caution statements, noting that the product contains ingredients that can cause skin irritation in certain indivduals and that the product must not be used for dyeing eyelashes or eyebrows, as it may cause blindness.

Fortunately for Sherri, 57, of Illinois, her reactions to hair dye, although quite unpleasant, have been relatively mild. Sherri (who asked that only her first name be used for privacy), has been bothered by hair color products for nearly 10 years. Before, she had been coloring her hair blond without any problem. Then, she decided to go darker. Every five weeks or so, as Sherri colors her shoulder-length hair at home, her scalp reddens and a hard, deep rash spreads across her neck, scalp and ears. Symptoms can last days after application.

Still, Sherri is determined to stick to her coloring regimen. “I don’t want go gray,” she says. “I’m not ready.” She’s working with a dermatologist to pinpoint her specific chemical allergy, and looking online for legitimately natural products that will work for her.

If you suspect or know you have a hair-dye allergy, trying to use workarounds like coating your scalp with vaseline is not recommended. Continued exposure just isn’t safe, and reactions can worsen with each exposure. Scheman emphasizes: “If somebody’s allergic to hair dye, they’re not going to be able to use the hair dye to which they’re allergic. Period.”

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If you’re a first-time shopper for hair-color products, bring along your magnifying glass and a chemistry degree. Only then will you recognize all the versions of the No. 1 culprit in allergic hair-dye reactions — paraphenylenediamine, or PPD — in the list of ingredients on the package.

As you browse among familiar brands such as Clairol and L’Oréal, you’ll find products containing PPD or the chemical para-toluenediamine sulfate, or PTDS. Although it’s chemically similar, PTDS is somewhat less likely than PPD to provoke an allergic reaction. A 2011 study in the journal Dermatitis found that nearly 60 percent of people who were allergic to PPD were able to tolerate PTDS hair dyes.

The chemical PPD is found in about 80 to 90 percent of hair dyes in salons and consumer products for use at home, says study author Dr. Andrew Scheman, an associate professor of clinical dermatology at Northwestern University.

Most so-called natural hair dyes on the market are really just gimmicks, according to Scheman. “They’re not natural at all,” he says. Like other hair dyes, he says, many brands that claim to be natural contain PPD or PTDS with a few extra botanical ingredients thrown in.

Scheman also sees patients with significant hair dye reactions. “They can be terrible,” he says. “Patients can have totally eroded, inflamed and raw scalps and facial skin. Sometimes it’ll go down on the neck, or even spread to other parts of the body.” A severe reaction resembles a severe case of poison ivy, he says, mostly concentrated on the scalp and facial area.

You can’t immediately assume hair dye is responsible for this type of reaction, Scheman says. Thorough testing is necessary to rule out shampoos, conditioners and hair-styling products with other ingredients, including fragrances, that can cause skin side effects. To pinpoint the chemical involved and determine safe alternatives, he says, your best bet is to find a patch-testing center that offers a complete hair-dye tray. Your local dermatologist can order a hair-dye tray if indicated.

Consumer Precautions

Although most people who dye their hair will do just fine, for those who are allergic, preventive measures can spare them the misery of an unexpected reaction. With customers new to coloring, some salons will do a patch test by applying a small amount of the product behind the ear or inside the elbow 48 hours before the actual hair-dyeing appointment, to observe whether signs of skin reaction such as itching, rashes or swelling appear at the sample site. If your salon doesn’t offer this walk-in testing, you should ask for it anyway to be on the safe side.

Similarly, DIY hair dyes advise testing a little bit of the product in advance before slathering it on your hair to make sure you’re not allergic. How many consumers actually follow pre-testing instructions is uncertain. “That is a little impractical, because as soon as you open that bottle of hair dye and mix the two chemicals together, you have to discard it within a matter of time,” Draelos says. “So it’s a required warning but I doubt that many consumers do that if they’re doing at-home hair dye.”

If you do notice early signs of a reaction, like scalp itching, you should suspect that you’re allergic. “Even though you apply a small amount of dye to a limited area, it’s not the same as dyeing your whole head,” Draelos points out. “Anybody who notices any eye swelling, itching or scabbing [following application of] a hair dye should discontinue the dye until they see a dermatologist.”

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If you’re not ready to call it quits with coloring your hair, you still have options. Allergy testing might show that you can tolerate certain commercial hair dye brands but not others. You could also turn to genuinely natural products, although you might not find them on your supermarket shelf.

“For people who are truly allergic to PPD, what we recommend that they do is use black-walnut hair dye, which is a stain,” Draelos says. “Of course, you can only go darker.” For those who’d rather be redheads, henna products are another possibility (unless you’re allergic to henna). “Many of the newer products actually combine henna with PPD-containing dyes,” she says. “But if you use a true henna, where you take the plant and crush it and retrieve the juice, the juice has to sit two or three days. The longer it sits, the darker the color.”

If you prefer prepackaged products, some brands, like Light Mountain Natural Hair Color, contain only botanical ingredients including henna, senna and indigo leaves. Pure henna (not mixed with PPD) is considerd to have a low allergy potential, although there have been cases.

If you’re determined to cover gray, certain store-bought brands might work. These are progessive dyes that contain lead acetate, often sold as men’s hair products. However, consumer groups have petitioned the Food and Drug Administration to remove lead-based hair dyes for concerns other than allergies, claiming that the lead exposure is toxic, with cancer-causing and other potentially harmful effects. (Members of the public can submit written or electronic comments to the FDA through June 5.)

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