If you’re having an allergic reaction right now, the first thing to do is assess how serious it is. Mild reactions like localized hives or itching can be managed at home with antihistamines. Severe reactions involving breathing difficulty, swelling of the face or throat, or dizziness require an immediate call to 911 and, if available, an epinephrine auto-injector.
How to Tell if It’s Severe
The difference between a mild and severe allergic reaction comes down to how many body systems are involved and how quickly symptoms escalate. A few hives on your arm after touching something irritating is a localized reaction. Hives spreading across your entire body, throat tightness, or a sudden drop in blood pressure is anaphylaxis, and it can be fatal without treatment.
Call 911 or get to an emergency room immediately if you notice any of the following:
- Swelling of your face, lips, tongue, or throat
- Difficulty breathing or swallowing
- Chest pain or tightness
- Hives spreading all over your body
- Tingling in your hands, feet, or lips
- Feeling weak, dizzy, or faint
- A sense of dread or feeling like something is very wrong
Skin symptoms like hives or flushing appear in 80 to 90 percent of anaphylaxis cases, but some of the most dangerous episodes have no skin involvement at all. A person can go into cardiovascular collapse with a rapid heart rate and dangerously low blood pressure as the only signs. If someone suddenly becomes confused, loses their voice, or develops noisy breathing (a high-pitched sound when inhaling), treat it as an emergency even if you don’t see a rash.
What to Do in a Severe Reaction
Use an epinephrine auto-injector if one is available. Don’t wait to see if symptoms improve on their own. Epinephrine is the only medication that can reverse anaphylaxis, and using it early is safer than using it late.
To use an EpiPen or similar auto-injector: hold it in your dominant hand with the needle end (usually orange) pointing down. Remove the safety cap with your other hand. Press the needle end firmly into the outer thigh, about halfway between the hip and knee. You can inject through clothing. Hold it in place for 3 seconds, then pull straight out. Massage the injection site afterward. Give the used auto-injector to paramedics when they arrive.
Even after using epinephrine, call 911. The effects of epinephrine wear off, and a second wave of symptoms is possible. While waiting for help, lie down with your legs elevated (unless you’re having trouble breathing, in which case sit upright). If you vomit, turn on your side. Don’t eat or drink anything.
Managing a Mild Reaction at Home
If your symptoms are limited to a patch of hives, mild itching, or a localized rash and you’re breathing normally, you can typically manage things without emergency care. An over-the-counter antihistamine is your first line of relief. Cetirizine (Zyrtec) and loratadine (Claritin) are good options that won’t make you drowsy. Diphenhydramine (Benadryl) works faster but causes significant drowsiness. For adults, standard dosing is one 10 mg cetirizine tablet or one to two 25 mg diphenhydramine capsules every six hours as needed.
If the reaction is on your skin from direct contact with an irritant, wash the area thoroughly with soap and cool water. A cold compress can reduce swelling and soothe itching. Calamine lotion, especially if chilled in the refrigerator first, helps with contact rashes. For more persistent or widespread contact dermatitis, a steroid cream can calm the inflammation. Over-the-counter hydrocortisone works for mild cases, though a prescription-strength steroid cream may be needed for stubborn rashes.
Keep an eye on mild reactions for several hours. If hives begin spreading beyond the original area, if you develop any swelling around your face or throat, or if you start feeling lightheaded, that’s a signal the reaction is escalating and you need emergency care.
What to Do After a Bee Sting
Insect stings are one of the most common triggers for sudden allergic reactions, and how you remove the stinger matters. Scrape it out using the edge of a credit card, a butter knife, or your fingernail in a flat, sideways motion. Don’t use tweezers or pinch the stinger, because squeezing can compress the venom sac and push more venom into the wound.
After removing the stinger, clean the area and apply ice. A mild sting reaction (pain, redness, and swelling limited to the sting site) is normal and doesn’t indicate an allergy. A sting that causes hives away from the sting site, facial swelling, or any breathing changes is a systemic reaction and should be treated as an emergency.
Why a Second Wave of Symptoms Can Happen
After a serious allergic reaction, symptoms can return hours later even without another exposure to the trigger. This is called a biphasic reaction, and it happens in roughly 1 to 20 percent of anaphylaxis cases depending on severity. One large registry study found an overall rate of about 16 percent. People whose initial reaction was very severe had the highest risk: 30 percent experienced a second wave, compared to just 7 percent of those with a mild initial reaction.
This is why hospitals typically monitor patients for several hours after treating anaphylaxis, and why you should go to the emergency room even if epinephrine resolved your symptoms at home. The second reaction can be just as severe as the first.
Follow-Up After a Serious Reaction
After an emergency room visit for anaphylaxis, you should leave with an epinephrine auto-injector prescription if you don’t already have one. Carry it with you at all times, not in a bag that might be across the room when you need it.
If you know what triggered the reaction, follow up with an allergist at your next opportunity. If the trigger is unknown, the standard recommendation is to see an allergist within 4 to 8 weeks. Testing can identify the specific allergen and help you develop an avoidance plan. Your allergist may also discuss whether you’re a candidate for desensitization therapy, which gradually trains your immune system to tolerate the trigger over time.
Make sure the people around you regularly (family, coworkers, close friends) know where your epinephrine is kept and how to use it. In anaphylaxis, you may not be able to inject yourself. Having someone nearby who can act quickly is one of the most practical things you can do to stay safe.