Allergy shots, a form of immunotherapy, help the body build tolerance to specific allergens by gradually desensitizing the immune system. Understanding potential reactions and their timing is important for patient safety. This article discusses typical reaction timeframes and offers guidance on post-shot monitoring.
Immediate Reactions After Allergy Shots
The most common reactions to allergy shots occur immediately at the injection site. These are local reactions, such as redness, swelling, or irritation where the shot was given. Such responses are expected as the immune system encounters the injected allergen, and they typically begin within a few hours and usually resolve quickly.
Due to the possibility of immediate reactions, patients are required to remain at the clinic for at least 30 minutes after receiving an allergy shot. This observation period allows medical staff to monitor for any adverse effects and provide immediate treatment if necessary. The 30-minute waiting period is consistently recommended, even after years of shots, because serious reactions can still occur.
Understanding Different Reaction Types
Reactions to allergy shots are categorized as local or systemic. Local reactions are confined to the injection site, involving redness, itching, or swelling. These reactions usually appear within a few hours and may persist for up to two days. Delayed local reactions can develop up to three days post-injection.
Systemic reactions are less common but involve a broader body response. These reactions extend beyond the injection site and might include symptoms like sneezing, nasal congestion, hives, widespread itching, or flushing. More severe systemic reactions can manifest as throat swelling, wheezing, difficulty breathing, or dizziness.
While most systemic reactions, including anaphylaxis, typically begin within 30 minutes, they can occasionally start later. Anaphylaxis is a rare, life-threatening reaction requiring immediate medical attention.
Post-Shot Monitoring and When to Get Help
After leaving the clinic, continue monitoring for symptoms for several hours and the rest of the day. Delayed reactions are possible. Avoiding vigorous exercise for a few hours after the shot can help reduce reaction risk.
If symptoms develop, assess their severity. Mild local reactions, such as redness or swelling at the injection site, can be managed with ice or an antihistamine. Inform your allergist if a local reaction is particularly large (e.g., larger than a 50-cent piece) or persists over 24 hours.
Signs warranting immediate medical attention include widespread hives, swelling of the throat, mouth, lips, or tongue, trouble breathing, wheezing, chest tightness, or feeling faint or dizzy. These indicate a severe systemic reaction. If you experience any serious signs, use an epinephrine autoinjector if prescribed, and call emergency services immediately. Communicate any unusual symptoms to your healthcare provider.