If your contact dermatitis is a type of allergic reaction, you’re likely to experience more severe signs, including burning, itching, and excessive dryness, Dr. Ogunleye says. A facial allergic reaction can also present as a red rash—again, depending on your skin color—which often spreads beyond the area where the product was applied; hives, a type of raised and itchy welt, are another common symptom. If you have an allergy, it may only take a very small amount of contact with the offending ingredient to cause a problem.

Some allergic reactions may also only occur when your skin is exposed to the allergen and the sun, which is called photoallergic contact dermatitis. Sunscreen, shaving cream, and perfume are all common causes.

Why do skin allergies often feel so sudden?

If it seems like your skin is having an allergic reaction out of nowhere, when it’s never happened before and you haven’t changed your routine, you’re probably not doing anything wrong. That’s often just how it goes: Allergies can develop when your skin becomes sensitized over time to whatever ingredient is causing the issue and this typically requires multiple exposures, Dr. Mancuso explains. So you might have no idea that you’ve been developing an allergy to something you’re using until it one day rears its inflamed, rash-y head.

Plus, allergic reactions usually don’t show up immediately; it could be hours or days after exposure before you see or feel any of the symptoms mentioned above, making it difficult to trace the cause. It could be triggered by something you’ve been using for a while and, therefore, assumed you had no issue with, for example. Or if you’re trying a new serum, say, with an ingredient that you previously became sensitized to, then you could have a reaction the first time you apply it.

You may also develop a rash somewhere other than the area where you originally applied the problematic product. For example, if you’re allergic to an ingredient in nail polish, your fingers may not react. But if you scratch your thin-skinned eyelid with a polished finger? That might leave you with allergic contact dermatitis around your eye—a connection that might be tough to make.

Additionally, things you ingest—like foods and medications—can also cause an allergic reaction on the face. If you think your angry skin could be connected to something other than a topical product, make note of that and let your primary care physician (PCP) or dermatologist (if you have one) know. They may refer you to an allergist, who can help you get to the bottom of your irritation.

How to treat an allergic reaction on your face

No matter how your reaction is showing up, the first thing you should do is stop using whatever product you suspect might have caused it. If you’re experiencing severe symptoms like a weak and rapid pulse, a swollen tongue or throat, trouble breathing, nausea, vomiting, diarrhea, or dizziness, you should seek immediate medical care—head to the emergency room, as these could be signs of a life-threatening allergic reaction called anaphylaxis.