Skin Allergy vs. Skin Reaction: How to Tell the Difference

I recently gave out a bunch of Osmia samples at a medical conference I attended in Big Sky, Montana. I figured some of my fellow physicians might appreciate a refreshing dose of Purely Simple Face Cream or a swipe of Lip Doctor after sitting in a dark conference room learning about shark bites and lightning strikes all day.

A few days later, my team received a rather spicy phone call from a nurse who had been at the conference and tried one of the samples. She said her skin had felt hot and become red after using it, and told my teammate Karla that the product should be “reported.”

I got her phone number and called her to apologize for the unpleasant experience—that’s never the story we want to hear about someone using an Osmia product. But even with educated formulation and meticulous ingredient selection, it simply isn’t possible to make a skincare product with a zero percent chance of causing irritation or a reaction. Because… humans. For all our scientific knowledge, we are still mysteries—even to ourselves. 

I decided to use the unfortunate incident as an opportunity to explain the difference between a skin reaction and a true skin allergy. They’re not necessarily the same thing, and knowing the difference can help you figure out what to do if your skin suddenly reacts to something. If you’re reading this because your skin is reacting to something right this minute, take a second to go wash your face gently with cool water, and apply a cool, wet, clean washcloth to your skin.

What Is an Allergic Skin Reaction?

A true allergic skin reaction, usually referred by physicians to as allergic contact dermatitis (ACD) or a Type IV Hypersensitivity Reaction, involves T-cell mediated hypersensitivity reaction after being exposed to something you have become sensitized to after a previous exposure. ACD accounts for about 20% of contact dermatitis. The classic examples are poison oak and poison ivy, although allergies to fragrance compounds, nickel, and some preservatives can cause allergic contact dermatitis as well. For a true allergic reaction, your body has to have encountered the substance and become sensitized to it previously in order to react to it on a subsequent occasion—even if you don’t remember ever having been exposed to it. In the case of poison ivy, for example, your body comes in contact with the oil of the plant, and you don’t react to it the first time, but your body recognizes it as a foreign substance and develops a chemical memory of it. The next time you’re exposed to it, your body recognizes it, and has specific cells that storm the scene to attack the intruder; this immune response is what causes itching, inflammation, and painful blisters. 

What Is an Irritant Skin Reaction?

An irritant skin reaction, often called acute irritant contact dermatitis (ICD), is actually more common than allergic contact dermatitis—it accounts for about 80% of contact dermatitis. ICD involves immediate irritation of the skin with the release of inflammatory mediators that can cause redness, burning, or stinging. It involves injury to the epidermal cells, which allows more of the irritating substance to penetrate the skin and triggers a local inflammatory response, increasing blood flow to the area (heat and redness) and putting out signals to immune cells that can cause swelling and burning or stinging. 

Delayed acute irritant contact dermatitis can occur with certain chemicals as well. In the realm of skincare, the best example of delayed ICD is with tretinoin, where redness and irritation can begin 8-12 hours after application of topical retinoid product. This is a common reason why some people (including the person writing this article) are not able to tolerate retinoids and end up using gentler alternatives. 

Allergy or Irritation: Can You Tell by the Symptoms?

Not necessarily, which makes it even harder to tell what’s going on when your skin reacts to something. While a few skin reactions have telltale appearances (like poison ivy), most involve more general symptoms like redness, swelling, and discomfort. Hives are rare in either case. 

Here are a few points that might help you distinguish between ACD and ICD: 

What Is Contact Urticaria Syndrome?

If ACD and ICD had a conceptual baby, it might be Contact Urticaria Syndrome (CUS). There are two types: one behaves more like an allergic reaction, while the other is more similar to an irritant reaction.

Immunologic contact urticaria syndrome is a Type I hypersensitivity reaction (a true allergy), which requires prior sensitization. A classic example would be a latex allergy, where someone has become sensitized to latex proteins, comes in contact with latex again, and has an immediate skin reaction, often involving hives (also known as urticaria). This type of hypersensitivity is histamine-mediated, and often responds well to antihistamines, although severe reactions may require more significant medical intervention. 

Non-immunologic contact urticaria syndrome (also known as a non-immunologic immediate contact reaction, because it may not involve hives) is not considered an allergy, and can occur on first exposure. It involves an immediate skin reaction—redness, warmth, swelling, itching, stinging, or burning—limited to the area of contact, and usually resolves within minutes to hours. Stinging nettle is one familiar example, but certain cosmetic ingredients and preservatives can also cause this kind of reaction. 

In the case of the nurse I mentioned at the beginning of this article, my hypothesis (though I have no way to prove or disprove this) is that her skin reacted to a part of the preservation system we use in some of our products, mostly likely the potassium sorbate (a close cousin of sorbic acid, which can cause skin reactions). Her description of immediate heat and redness sounds more consistent with a non-immunologic immediate contact reaction than with classic allergic contact dermatitis.

Potassium sorbate is a very commonly used skincare ingredient, and most skin types tolerate the low concentration we use extremely well. Based on reports we’ve received since introducing the current Purely Simple Face Cream formula in 2021, fewer than 0.5% (half of one percent) of our customers appear to experience this kind of reaction. (That number is our own real-world estimate, not a published population-wide reaction rate.)

Does Sensitive Skin Mean You Have Skin Allergies?

Not necessarily, although the two often like to play in the sandbox together. If you have sensitive skin, your barrier function may be impaired, which can make your skin more reactive in general. When the skin barrier isn’t working properly, potential allergens can penetrate more easily, which may increase the likelihood of sensitization and allergic reactions. It’s kind of a mess, honestly. And, to complicate things further, your skin may be more likely to react to something if you’re stressed, if you’ve gotten lots of sun that day, or if you’ve just taken a steaming hot shower.

If your skin is reacting to things regularly, it’s worth having patch testing done by an allergist or a dermatologist. There, the doctor will apply common allergens to your skin and leave them there for several days. When you go back, the patches get removed and your skin reaction gets measured. If you don’t react to the patches, your skin reaction may not be a true allergy—or at least not a common one. 

Can Skincare Ingredients Cause Skin Reactions?

Absolutely, and it doesn’t matter if the product is synthetic or natural; just as a mango or a peanut can cause an allergic reaction, so can almost any skincare ingredients derived from the natural world. Commonly used skincare ingredients, like phenoxyethanol or potassium sorbate, can cause skin reactions in some people, even when used at very safe concentrations. While skin reactions are fairly rare, given the number of people who use cosmetics every day, some of the skincare ingredients that have been known to cause reactions are listed below. 

• Fragrance (often listed as “parfum”) and some essential oils (especially oak moss, cinnamon, mint, and raw Balsam of Peru resin)

• hydroxyisohexyl 3-cyclohexene carboxaldehyde, also known as HICC or Lyral (fragrance ingredient used in loads of mainstream deodorants, banned in the EU)

• Methylisothiazolinone (common preservative)

• Oxybenzone (sunscreen ingredient)

• Phenoxyethanol (extremely common preservative in natural skincare products)

• Triclosan

• Sodium benzoate

• Sorbic acid

• Hydrolyzed wheat protein

Can you suddenly become allergic to a product you've used for years?

Sadly, yes. You can tolerate an ingredient for years before your immune system becomes sensitized to it. Sensitization may be more likely when the skin barrier is damaged or inflamed, because potential allergens can penetrate more easily. Once sensitization occurs, even small amounts of the ingredient may trigger allergic contact dermatitis in the future.

This actually happened to me when I had an allergic reaction to a mango that caused my lips to blister and peel for weeks on end. During that compromised period, I developed an allergy to ricinoleic acid, a compound found in castor oil, and had to develop a castor-free lip balm (our Lip Doctor) to heal my lips. 

What Should You Do If You Have a Reaction to Skincare?

Keep calm! Consider washing the product off with cool water and applying a cool washcloth to your skin for a few minutes. Resist the urge to apply soothing products, because they could actually make things worse. If you feel your skin getting warm again, apply a fresh, cool cloth, and repeat as needed. If you have extensive hives, a feeling of swelling in your mouth or throat, or any difficulty breathing, you should call 911 immediately and consider using an EpiPen or taking an antihistamine while you wait for medical professionals to arrive. 

If your skin ever reacts to a skincare product—Osmia or otherwise—don’t assume it means you’ve developed an allergy. Stop using the product, give your skin a chance to settle, and pay attention to the timing and symptoms. And if you ever do have an unexpected reaction to an Osmia product, please reach out to us. Reactions are uncommon, but when they happen, we want to hear about them—and we’ll always do our best to help you figure out what may have happened.

With love and a nice cold compress, 

Resources:

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