Symptoms, Common Triggers and Emergency Signs
Hives are one of the most recognizable signs of an allergic reaction. They appear when the immune system releases histamine after exposure to something it mistakes as dangerous. Most hives are not allergic, but when they are, timing is usually the clue.
Signs of an Allergic Hive Reaction
Welts usually appear within minutes to two hours after contact with the allergen and may be accompanied by itching, flushing and lip or eyelid swelling.
Common Allergic Triggers
- Foods: see food allergy hives
- Medicines such as penicillin and sulfa drugs
- Insect stings
- Latex
- Contact with plants or animals
Mild Vs Severe Reactions
Mild reactions involve only the skin. Anaphylaxis involves multiple body systems, such as breathing, circulation or digestion, and requires immediate epinephrine and 911.
What to Do
- Move away from the trigger.
- Take an antihistamine for mild skin symptoms.
- Watch closely for other symptoms for several hours.
- Tell your doctor; testing can confirm allergy.
See are hives dangerous.
When to Call 911
Call 911 right away if hives or swelling occur with difficulty breathing or swallowing, a tight or closing throat, a swollen tongue, lips or face, wheezing, faintness, or a sudden feeling of impending doom. Use an epinephrine auto-injector first if one has been prescribed to you, then call for emergency help.
When to See a Doctor
See a doctor if your symptoms last more than a few days, keep coming back, cover large areas, or interfere with sleep or daily life. Dr. Tiffany Young’s Hives Treatment Center in San Francisco offers online and in-person consultations for patients with allergic hives.
Related Reading
You may also find these guides helpful: causes of hives and hives symptoms.
Frequently Asked Questions About Allergic Reaction Hives
How quickly do allergy hives appear?
Typically within minutes to two hours.
Are all hives allergic?
No. Most chronic hives are not allergic.
Can I develop a new allergy as an adult?
Yes.
Get Relief for Your Hives
An allergist can confirm triggers and prepare an action plan. Visit our hives treatment page to see the latest treatment options for your outbreak.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. If you think you are having a medical emergency, call 911.
