Dermatologist's Take
Non-drowsy antihistamines like cetirizine, loratadine, and fexofenadine are the first-line treatment for hives, and they are safe and easy to use. If a normal dose is not enough, a doctor may raise it up to four times. Older, sedating options work but cause drowsiness.
At a glance
- AKA: H1 blockers; includes cetirizine (Zyrtec), loratadine (Claritin), fexofenadine (Allegra), diphenhydramine (Benadryl), and hydroxyzine
- Drug Class: H1 antihistamine (blocks the chemical histamine)
- Rx or OTC: Most are over-the-counter; hydroxyzine is prescription only
- Typical Dose: One standard dose by mouth per day; a doctor may raise it up to 4 times for hives
- Time to Work: Within 1 to 2 hours for a single dose; full effect on hives over days to weeks
- Evidence Level: Strong for hives; recommended as first-line by allergy and skin guidelines
What is it?
What is it text.
How it works
When your body reacts to a trigger, cells release a chemical called histamine. Histamine causes the itching, redness, and swelling that make up the welts of hives. Antihistamines block histamine from attaching to its receptors on nearby cells, which lowers itching and swelling. Second-generation antihistamines are built to stay out of the brain, so they cause little or no drowsiness. First-generation ones cross into the brain, which is why they make many people sleepy.
What it treats
How it's typically used
- Second-generation (non-drowsy) options are usually tried first: cetirizine (Zyrtec), loratadine (Claritin), levocetirizine (Xyzal), and fexofenadine (Allegra). These are taken once a day.
- Up-dosing for hives: Guidelines say that if a standard dose does not control hives, a doctor may raise the dose up to four times the normal amount. This should only be done under a doctor's guidance, not on your own.
- First-generation (sedating) options: diphenhydramine (Benadryl) and hydroxyzine also work but cause drowsiness. Hydroxyzine needs a prescription. These are often used at night or for short-term relief.
- Take with water. Fexofenadine works best when not taken at the same time as fruit juice.
This is educational only. Follow your doctor's advice or the product label.
Common side effects
Second-generation (non-drowsy):
- Mild drowsiness (a bit more likely with cetirizine)
- Dry mouth
- Headache
First-generation (sedating, like Benadryl and hydroxyzine):
- Strong drowsiness
- Dry mouth and dry eyes
- Blurred vision
- Constipation
- Trouble urinating
- Confusion, especially in older adults
Serious side effects
- Fast or irregular heartbeat
- Severe drowsiness or confusion
- Trouble urinating
- Signs of an allergic reaction to the medicine itself (rash, swelling of the face or throat, trouble breathing)
Call a doctor or seek emergency care if these happen. Very high doses of sedating antihistamines can be dangerous, especially in children and older adults.
Who shouldn't take it
- Do not use an antihistamine you have reacted to before.
- Use sedating antihistamines (Benadryl, hydroxyzine) with caution if you are an older adult or have glaucoma, an enlarged prostate, or trouble urinating.
- Hydroxyzine should be avoided by people with certain heart rhythm problems (a long QT interval).
- Talk to a doctor before using higher-than-normal doses.