Antihistamines are a common treatment option for hives, but they may not be effective for everyone. They may also stop working over time. Identifying hives triggers and avoiding them may help prevent flare-ups.

Hives are an allergic skin reaction that appears as raised patches, bumps, or a combination of both. They may also be itchy or inflamed. Healthcare professionals may refer to hives as urticaria.

Doctors treat hives with several different therapies, including antihistamines.

This article discusses why antihistamines may not work, hives triggers and how to identify them, other treatment options, how to manage hives at home, and when to speak with a healthcare professional.

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Doctors often prescribe antihistamines for hives. Antihistamines are a type of medication that blocks histamine, which is a substance the immune system releases when it detects a potential threat to the body. Histamine causes several effects in the body including inflammation, itchy skin, and flushing.

Researchers have suggested two possible reasons that antihistamines may not work: not taking medications as directed and insufficient dosing.

An older 2009 study noted that previous studies on antihistamines for chronic hives reported between 44–90% effectiveness.

The study authors speculated that part of the reason antihistamines may not work could be that some people take them on an as-needed basis or when symptoms occur. They suggested that a person should take antihistamines every day for consistent results.

However, the exact dose and how often a person should take them depends on the medication’s half-life, which is the time it takes for the medication’s active substance in the body to reduce by half.

In a 2023 review of studies, researchers stated that second-generation antihistamines are not always effective at treating chronic spontaneous hives. Their findings indicated that people may need to take up to two times the standard antihistamine dose for better efficacy. However, they suggested that future studies into the safety and efficacy of increasing the dose are necessary.

Similarly, a 2017 study suggested that updosing antihistamines dosage fourfold may help reduce the need for a third line of therapy for chronic spontaneous urticaria by about 49% with a limited increase in reported side effects.

Trigger identification and management can play a role in helping a person find relief from chronic hives. Triggers are anything that causes hives to occur. They can vary between people.

Some possible causes and triggers of hives can include:

While many people can identify the underlying cause of their hives, experts estimate that millions of Americans develop hives during their lifetime with no known cause. Some of these individuals may develop chronic spontaneous urticaria, which healthcare professionals define as hives lasting for 6 or more weeks.

A person should consider writing down when they have a flare and include information such as what they were doing, eating, and so on. This may help the person narrow down or figure out what may be triggering their hives.

The table below shows approximate times from trigger exposure to hive development.

Potential triggerTime for hives to appear
additives, such as preservatives and colorings in various productswithin 12–24 hours
coldimmediately after starting to warm up from cold conditions or immediately after entering an air-conditioned building or walking near a freezer case
food within about 1 hour of eating the food
certain foods (if someone has a latex allergy)within 12–24 hours
medicationsfrom immediately to potentially years later
ultraviolet lightwithin minutes
heatwithin minutes
pressure on the skin immediately, or within 4–24 hours later
touching certain animals, chemicals, or plantswithin minutes
adrenaline (which the body releases due to exercise and stress, for example)appear quickly and last about 30–60 minutes

Antihistamines are one possible treatment for hives. Dermatologists and other doctors may prescribe or recommend a person take one or more other medications to help treat and prevent hives. These can include:

  • corticosteroids
  • anti-itch cream or lotion
  • autoinjector (EpiPen)
  • phototherapy, which involves a healthcare professional shining ultraviolet light on areas of the skin
  • omalizumab (Xolair)

If antihistamines or any of the treatments above are not working, a doctor may recommend other medications, such as cyclosporine or hydroxychloroquine, which help calm the immune system.

In addition to treatment options a doctor may offer, a person can take steps to help manage their hives at home. Some self-care tips for hives include:

  • applying a cold compress to the skin
  • taking a colloidal oatmeal bath
  • wearing 100% cotton, loose fitting clothes
  • using gentle cleaners without fragrances
  • keeping track of when hives occur
  • avoiding scratching skin that itches
  • taking lukewarm baths and showers

It is recommended that a person consider talking with a doctor if they develop hives that do not go away. A doctor can help develop a treatment plan and help a person figure out what may be causing the hives.

If treatments do not appear to help, it is important that a person discusses this with a healthcare professional who can make any necessary changes to their treatment plan such as adjusting medications.

It can be helpful for a person to consider keeping a journal of when their hives appear and bringing it along to their doctor’s appointment. It can be helpful for a person to record important information about the hives, such as when they occur, what type of food the person was eating, any other possible triggers, the severity of the hives, and how long they last.

Some research suggests that antihistamines for hives may not work if the dose is not high enough or a person does not take the medication daily or as a doctor prescribed.

Working out what is causing the hives may help direct treatment. A doctor can provide several different treatment options for a person, such as corticosteroids, phototherapy, and anti-itch creams.

If antihistamines or other treatments do not work, it is important that a person discusses this with a doctor so they can recommend other options.