Clearly you would know if you had an allergy, of course. It’s all runny noses, blurry vision, and constant itching, right? Well, no. Here are a few signs you may not have noticed ¦ or, more likely, noticed but didn’t realize what they signified:

Dizziness: Common among electromagnetic hypersensitivity sufferers. Apparently, the electromagnetic waves generated by electronic devices and, thus, by pretty much all of modern society, can affect some people, causing nausea and dizziness. The phenomenon isn’t widespread, and some scientists aren’t even sure yet that it actually exists.

Skin Tumors: This shows up most commonly as a reaction to tattoos with red ink. The body recognizes the ink as a foreign substance and triggers a response, except it’s a little overzealous in this case. It seems to be unclear why the red ink is the most virulent.

Black Spots: In some rare cases of exposure to poison oak or ivy, shiny black spots appear on the skin in place of the usual rash and hives. It eventually peels off without affecting the skin in any other way. The resin the plants produce seems to be responsible for pooling and adhering to the skin and, in some cases, clothing of the victim.

Swollen Tongue: Some fruit proteins have very similar chemical makeup to the substances found in hay pollen, and the immune system attacks it in a similar way. So, not quite a symptom of allergy, but a symptom of an allergy that isn’t actually happening.

Headaches: Nasal symptoms can collectively act as a magnet for migraines or milder headaches, even in the absence of a runny nose or even a stuffy head feeling.

Itchy Ears: Similar to eczema, but in the ear canal itself, or possibly just swelling of the tissues. Treatable by antihistamines, but a puzzling symptom nonetheless.

Diarrhea: Similar to the swollen tongue symptom; basically the immune system recognizing an invader but taking far more drastic action than is necessary. In this case it tends to be grains and produce being mistaken for ragweed or grass pollen.

Sore Throat: With a stuffy nose, your nighttime breathing is generally through your mouth, which will dry the mucous membranes out. In turn, that will lead to a raw and sore throat in the morning, since there is no longer any protective coating inside. It will replenish itself soon after you wake up and start to go about your day.

Behavior Changes: A poor night of sleep owing to breathing issues and general discomfort can easily lead to irritable behavior the next day.

Facial Eczema: Common among nickel-allergic sufferers, the mild facial rash exactly where the phone meets the skin frequently gets dismissed as an eczema outbreak instead of the metal-contact dermatitis it really is. Diagnosis is complicated by the fact that the rash may show up as much as a week after exposure, so even if phone use is curtailed, the cause may go undetected.

Raised Skin: Normally henna tattoos are no cause for alarm. A black variant, however, frequently uses a type of hair dye that can easily irritate the skin and induce allergic reactions, blistering, and potentially scarring the skin in the shape of the ordinarily temporary tattoo. The hair dye, incidentally, is okay for use in hair, but if you’re allergic to it in henna, you’re probably allergic to it by itself.

Loss of Consciousness: This is a pretty worrisome symptom, in any case, but it can be the culmination of a rapid onset of anaphylaxis, a medical term for a severe, life-threatening allergic reaction. Swift action must be taken to save the victim; many sufferers carry emergency medication and an applicator with them at all times.

Baboon Syndrome: Very much what it sounds like: the buttocks, anus, genitals, and inner thighs are afflicted with an intense red rash. It can be itchy and painful, but it’s not considered debilitating. Metals such as mercury or gold can trigger an outbreak, as can certain antibiotics.

Remember, allergies can develop later in life, and severe ones can be deadly. Learn the common symptoms and keep these in mind. The fact remains that these are remarkable largely because they are unusual. Don’t assume that because you have a headache, you can’t have shellfish anymore. Get the tests done and verify what precautions you need to take to keep enjoying life.