Here's an interesting piece from yesterday's Wall Street Journal:
                      Surprise Allergies to ‘Natural’ Skin-Care Products

April 18, 2016 1:11 p.m. ET

Andrea Salinas for years used lavender-scented deodorant, figuring the “all-natural” product was healthier than commercial brands. She also used lavender oil as a body spray.

Recently, Ms. Salinas, a clinical social worker in San Francisco, started breaking out with a red, itchy rash that started in her underarm area and spread across her torso. Tests by a dermatologist turned up an unexpected culprit: She had developed an allergy to lavender.

The 44-year-old switched to a commercially available deodorant. “I love the smell of lavender,” she says, but now “there’s none whatsoever” in her house.

Health-conscious consumers increasingly have been snapping up lotions, soaps and other personal-care products drawn from plants and other biological sources. Some people also are drawn to marketing pitches that the products aren’t tested on animals. Sales in the U.S. of high-end, facial skin-care products marketed as “natural” grew more than 25% between 2013 and 2015, according to market-research firm NPD Group Inc. In other places, including in Europe, natural is a common marketing pitch among many leading brands.

Allergic contact dermatitis can be caused by a wide variety of substances, including poison ivy. Gauging how many people suffer from allergies to botanical ingredients in personal-care products is difficult. A group of 14 specialized dermatologists, known as the North American Contact Dermatitis Group, tracks which substances cause allergic reactions in its patient testing.

Many of the most common triggers of allergic contact dermatitis aren’t associated with organic-style products, such as the metal nickel and antibiotics neomycin and bacitracin. But more than 10% of people the group tested reacted to fragrances—many of which have botanical sources—making scents the second-biggest trigger of the condition in the tests.

The dermatologist group also sees allergies to certain natural oils, such as ylang-ylang and tea tree oil, which each sparked reactions in about 1% of people, according to Erin Warshaw, a member of the group and a professor of dermatology at the University of Minnesota in Minneapolis.

Patients often assume plant-derived oils and balms are safer than traditional alternatives, Dr. Warshaw says. They may even use them to treat a rash, which might make it worse. “There’s a lot of denial it could be causing the problem,” says Dr. Warshaw. “It’s like putting poison ivy on poison-ivy” rash.

Propolis, derived from bees, is another potential allergen. It is sometimes called bee glue and can be found in lip balm and other products. Some people also react to substances from the Compositae family of plants, a large group that includes camomile and chrysanthemum.

Christina Boland, a 42-year-old writer in Sierra Vista, Ariz., switched to products billed as all-natural after she learned that allergies to certain chemicals were causing her chronic rashes. She started mixing her own lotion and using shampoos and soaps made from organic ingredients.

Instead of going away, her condition worsened. Her body erupted in red, bumpy patches so itchy that she had to sleep with ice packs next to her skin, she says. Extensive testing at the Mayo Clinic’s Scottsdale, Ariz., campus revealed that Ms. Boland was reacting to botanical substances including tea tree oil, rosemary and propolis.

“I literally had to change everything I cleaned with, everything I put on my body,” Ms. Boland says. Now, she carefully selects products that her dermatologist says contain none of her allergens. She orders soap, shampoo and other items from specialized vendors.

Doctors say that it can be difficult to pinpoint the source of a skin reaction. People can use a product for years before they are sensitized enough to develop allergic contact dermatitis, making the sleuthing even more challenging. Jasmine is highly fragrant and can be found in products including bath oil, deodorant and perfume. Photo: Getty Images

Dermatologists generally use “patch tests,” which involve applying sticky sheets lined with spots of different allergenic substances to a patient’s skin for a few days. Many dermatologists use a standard array of 36 substances that may leave out many of the less-common botanicals. Specialists who focus on contact dermatitis may test for a broader list of potential causes, in some cases more than 100.

Patients can try a simple test of products that stay on the skin on their own, by dabbing of bit on the same spot for a few weeks to see if the area breaks out, suggests Bruce A. Brod, a clinical professor of dermatology at the University of Pennsylvania. “I tell patients, ‘eat organic, don’t necessarily put it on your skin,’” he says.

Avoiding known allergens can be tricky. Botanicals often have multiple names. And manufacturers in the U.S. aren’t required to list specific substances used in scents. “If a plant is used as a fragrance, they don’t have to tell you it’s there,” says Patricia Norris, an assistant professor of dermatology at Oregon Health & Science University, in Portland.

Dermatologists say the number of botanical substances used in personal-care products keeps growing. “It challenges my knowledge of Latin,” says James A. Yiannias, the Mayo Clinic dermatologist who treated Ms. Boland. “Every day I’m encountering ingredients” he hadn’t previously seen in skin-care products.

Dr. Yiannias serves as medical director for a website, skinsafeproducts.com, that helps patients find products that won’t trigger their allergies. The American Contact Dermatitis Society also maintains a database of products, which can be accessed by patients who have been treated by a physician who is a member of the society.