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How Can You Tell If You’re Having an Allergic Reaction?

How Can You Tell If You’re Having an Allergic Reaction?

As outdoor allergens continue to ramp up, seasonal allergy sufferers are bracing themselves for a return of their symptoms. But many other people deal with the discomfort of allergies seasonally or year-round — without even knowing it

Allergy symptoms can vary widely, so they are often mistaken for other illnesses. And mild allergies can be easy to ignore altogether. However, even mild allergies can become more serious with repeated exposure. This makes it important to recognize and treat symptoms when they occur.

Many people with mild allergies might not be aware that these common symptoms could stem from an allergic reaction.

1. Sinus discomfort

When most people think of allergies, sinus symptoms come to mind first. Common symptoms include a runny or stuffy nose; watery, swollen or itchy eyes; sneezing and nasal congestion. These are often seasonal, but for two-thirds of allergy sufferers, they persist year-round. If you experience sinus symptoms for an extended period or if they worsen seasonally, they may be linked to an undiagnosed allergy.

2. Trouble breathing

Allergens such as ragweed, pollen, dust mites and animal dander can trigger asthmatic symptoms in some people. If you experience unexplained wheezing or shortness of breath, you may be having an allergic reaction. Of course, asthma can have many triggers unrelated to allergens, such as physical activity. Your physician can help you determine the causes of your specific case.

3. Rashes

Skin irritation is a tell-tale sign of many allergies. Some people experience eczema, which causes dry, red and itchy patches of skin. Other people may break out in hives — red, itchy welts that generally disappear quickly. However, if your hives last longer than 24 hours, you should consult a physician.

4. Swelling or numbness

In many cases, an untreated food allergy may cause swelling of the lips, face or tongue. Tingling or numbness in the mouth is also possible. These reactions generally begin soon after eating. Keep in mind, though, that you might only be allergic to one ingredient in the food. Or, the food may have been cross-contaminated with traces of a different allergen, such as peanuts or tree nuts. Your physician can administer an allergy test to help you narrow it down.

5. Digestive problems

If you experience abdominal pain, diarrhea, nausea or vomiting soon after eating, food allergies are one possible cause. While many of these symptoms overlap with food intolerances, it is important to note that a food allergy can be triggered even after eating even tiny amounts of an allergen.

6. Anaphylaxis

Anaphylaxis is a severe reaction to an allergen and requires immediate medical attention. This serious condition can cause throat constriction, a sudden drop in blood pressure, a rapid pulse, dizziness or fainting. If you or a loved one experience anaphylaxis, call 911 immediately.

If you suspect that you might have undiagnosed allergies, making an appointment with your primary care physician at Keck Medicine of USC can help you be proactive about your health and enjoy more symptom-free days. To schedule an appointment, call (800) USC-CARE or visit

Keck Medicine of USC
Univeristy of Southern California
Keck Medicine of USC
Keck Medicine of USC
Keck Medicine of USC is the University of Southern California’s medical enterprise, one of only two university-owned academic medical centers in the Los Angeles area.