Sensitive skin is a pain—sometimes literally—and for skin allergy sufferers, contact with an allergen causes an itchy red rash that may last for weeks. Common skin care products such as soaps, serums and lotions (often what we hope will soothe painful skin) can trigger or worsen the irritation.

Sufferers in search of gentler skin care products may turn to "natural" options, hoping they'll live up to the claims of an even, healthy-looking complexion. But are these products less likely to cause skin irritation?

To answer this question, Stanford Medicine researchers examined the websites of three national grocery and drug store chains, seeking skin care products labeled as "natural." They then scoured their ingredient lists to determine whether the products contained common skin allergens.

Stanford Medicine dermatologist Gordon Bae, MD, and medical student Haiwen Gui discussed the results of the study, which was published in JAMA Dermatology last month, and what it means for consumers.

Many skin care products are marketed as natural, implying that they're somehow better, safer or gentler on skin than other products. What does it actually mean when a product is labeled 'natural?'

Bae: Most people think of natural products as containing fewer synthetic ingredients. These products may use ingredients such as minerals, herbal extracts or plant oils instead of their synthetic counterparts. But the Food and Drug Administration doesn't have an exact definition of "natural," so consumers don't have a clear idea of what they are getting when manufacturers label their product as natural.

Gui: On the major retail websites we analyzed, there's a separate, well-marketed group of products that are labeled as "natural," "healthy for your skin" and "good for people who have sensitive skin." But those labels can be misleading since there aren't any guidelines or oversight.

Can contact with natural ingredients cause skin problems, or even an allergic reaction?

Bae: Yes, absolutely. One of the most prevalent skin diseases is contact dermatitis, which is an itchy rash caused by skin contact with an irritant or allergen. For example, if you're using a facial moisturizer that contains an essential oil you're allergic to, you'll develop itchy red patches within a day or two of application. In the U.S., contact dermatitis accounts for around $1.5 billion in medical costs each year. It's a pretty common problem.

We often prescribe topical steroids to calm down the itchy rashes, but if you're very sensitive, you need exposure only once every three weeks to keep the allergic reaction going. It causes a lot of misery for patients because these allergens are so prevalent in natural skin care products that people end up getting exposed quite often, even if they stop using the product that caused the problem and switch to a new one.

You examined more than 1,700 'natural' skin care products looking for skin allergens. What did you find?

Gui: Our study showed that more than 94% of the products contained at least one known contact allergen. And 90% had an ingredient ranked in the top 100 most clinically prevalent allergens—in other words, the allergens that most commonly affect patients.

Bae: The most common allergen we found, and the one most likely to cause allergies, is fragrance. "Fragrance mix" was listed as an ingredient in 36.6% of the products. Consumers can check the ingredients for limonene, eugenol and hexyl cinnamal, among others, which are commonly used for fragrance in natural products.

What should consumers keep in mind when shopping for a skin care product that's gentle on sensitive skin?

Bae: If you have sensitive skin, or if you are planning on giving something to someone who has sensitive skin, rather than looking for products that are labeled as natural, clean or organic, try to get products that are labeled as fragrance free or hypoallergenic.

Gui: It's also really important to increase consumer awareness about how difficult it can be to interpret what labels like "natural" mean, in terms of the safety and benefits, when they shop for skin care products. We need clear regulatory guidance for natural products so consumers aren't led astray.