You started a weekly injection prescribed for weight, and about an hour after the first one your face went hot and hives came up across your neck. By evening they had gone. Two first-aid lists cover what happened: the signs of a severe allergic reaction, which are a 911 call, and the reactions people on this kind of medicine report most often, which are a message to the prescriber. Several of the same words sit on both. What separates them is how fast it came and which parts of you it reached, and both of those you can check yourself.
A severe allergic reaction usually arrives within seconds or minutes, and it reaches breathing, swallowing, the voice or the face. A few hives over the neck and face, with the nose and eyes involved, is the mild entry. Hives all over is on the severe list, so how much of you is covered matters as much as which part. If difficulty breathing, swelling of the face, eyes or tongue, or tightness in the chest is happening right now, call 911; MedlinePlus's first-aid line is not to wait and see whether it gets worse. If none of that is happening, tell your prescriber about the hives today rather than at your next appointment.
Which of your signs are on both lists
Four signs are on both lists: nausea, vomiting, diarrhea and abdominal pain. The signs of anaphylaxis, printed in full, are abdominal pain, feeling anxious, chest discomfort or tightness, diarrhea, difficulty breathing, coughing, wheezing or high-pitched breathing sounds, difficulty swallowing, dizziness or lightheadedness, hives, itchiness, redness of the skin, nasal congestion, nausea or vomiting, palpitations, slurred speech, swelling of the face, eyes or tongue, and unconsciousness.
The reactions reported most often by people taking one of the FDA-approved products in this class include nausea, diarrhea, vomiting, constipation, abdominal pain, indigestion, injection site reactions, fatigue, burping, hair loss and reflux. Hypersensitivity reactions are on that list as well, which is the label's term for an allergic one.
Matching what you feel against either list therefore puts you on both.
How fast it came, and which parts of you it reached
How fast it came and which parts of you it reached are the two things that separate a severe reaction from a mild one. Anaphylaxis develops quickly, often within seconds or minutes. Below is a selection from each of the two first-aid lists — the items a reader is most likely to be looking at in the first hour, not the whole of either. What changes between the columns is which part of the body is involved, and how far it has gone.
| Listed as a mild allergic reaction | Listed as a severe one |
|---|---|
| A few hives, especially over the neck and face | Difficulty breathing, wheezing |
| Itching | Swelling of the face, eyes or tongue |
| Nasal congestion | Chest discomfort or tightness |
| Rashes | Nausea or vomiting |
| Watery, red eyes |
An hour's delay does not settle it. Minor skin rashes and hives from a drug allergy may come right away or hours after a dose, so a gap of an hour is ordinary for that kind of reaction. What the severe end does is arrive fast — often within seconds or minutes — which is why the signs matter more than the clock.
Most side effects of medicines are also not due to an allergic reaction in the first place, which is why the same four words turn up on an ordinary reactions list and on an emergency one.
For a hypersensitivity reaction, the instruction on one of these products is to seek medical attention promptly and stop using it. What happens to the prescription after that is decided by whoever prescribes it, working from your account of what happened — which is why the time it started and how long it ran are worth writing down while you still have them.
What to do while it is happening, and who to tell after
What to do while it is happening turns on one question: whether breathing, swallowing or the face is involved. If any of them is, call 911 and do not wait to see if the reaction is getting worse. A severe allergic reaction in the past is a reason to make that call at the first sign rather than the third.
While help is on the way, the first aid is to have the person lie flat, raise their feet about 12 inches, and cover them with a coat or blanket. If emergency allergy medicine has been prescribed to them and is within reach, help them take or inject it at the start of the reaction. Nothing goes in the mouth of someone who is having trouble breathing, and the pillow comes out from under their head, because it can block the airway.
If breathing, swallowing and the face are all clear, the call goes to your provider instead: contact your provider if you are taking a medicine and seem to be having a reaction to it. Vomiting that carries on past the first evening is a different problem with its own timings, and it becomes urgent when you cannot keep fluids down.
Whoever picks up will ask what you took and when, the time the signs started, which signs, whether they are still going, and whether this was the first one. Keep the carton it came in where you can read it, because they will want the name printed on it rather than a description of what it looks like.
If it is happening now
- Call 911 for difficulty breathing, wheezing, swelling of the face, eyes or tongue, chest tightness, difficulty swallowing, slurred speech, faintness or collapse.
- Make that call at the first of those signs, rather than after watching to see where it goes.
- Lie flat with your feet raised and stay warm while you wait.
- Take or inject emergency allergy medicine at the start of the reaction, if one has been prescribed to you and is within reach.
- Keep food and drink away from anyone who is struggling to breathe, and take the pillow out from under their head.
- For hives, itching, a rash, a stuffy nose or watery eyes on their own, message the prescriber today and give the time it started.
- Note the time it started, the time it settled, and what you took, before you have to repeat it to a third person.
Once a reaction has settled, your account of it is the whole record — there is no test that recovers it afterwards. So what the prescriber works from is three things: the time it started, which parts of you it reached, and how long it took to go. Write those three down tonight, while you still have them, rather than reconstructing them at the next appointment.
