What happens if you take antihistamines for a long time

What are the long term effects of taking antihistamines?

Antihistamines are typically separated into sedating (first generation) and nonsedating (second generation) forms, based upon their central nervous system effects, the nonsedating agents being less likely to cross the blood-brain barrier. In addition, some antihistamines have additional anticholinergic, antimuscarinic or other actions. Antihistamines are some of the most commonly used drugs in medicine, and most are available in multiple forms, both by prescription and in over-the-counter products, alone or combined with analgesics or sympathomimetic agents. Common uses include short term treatment of symptoms of the common cold, seasonal allergic rhinitis (hay fever), motion sickness, nausea, vertigo, cough, urticaria, pruritus and anaphylaxis. Sedating antihistamines are also used as mild sleeping aids and to alleviate tension and anxiety. Many antihistamines are also available in topical forms, as creams, nasal sprays and eye drops for local use in alleviating allergic symptoms. Nonsedating antihistamines are typically used in extended or long term treatment of allergic disorders, including allergic rhinitis (hay fever), sinusitis, atopic dermatitis, and chronic urticaria.

Antihistamines have several adverse side effects which are related to their antihistaminic actions. Side effects are, however, usually mild and rapidly reversed with stopping therapy or decreasing the dose. These common side effects include sedation, impaired motor function, dizziness, dry mouth and throat, blurred vision, urinary retention and constipation. Antihistamines can worsen urinary retention and narrow angle glaucoma.

Antihistamines rarely cause liver injury. Their relative safety probably relates to their use in low doses for a short time only. The nonsedating antihistamines, however, are often used for an extended period and several forms have been linked to rare instances of clinically apparent acute liver injury which has generally been mild and self-limiting; the antihistamines most commonly linked to liver injury have been cyproheptadine, cetirizine and terfenadine (which is no longer in clinical use).

http://livertox.nih.gov/Antihistamines.htm

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Cetirizine - Brand names: Allacan, Benadryl Allergy, Piriteze Allergy, Zirtek Allergy

If you or your child have been prescribed cetirizine, follow your doctor's instructions about how and when to take it. If it is from a pharmacy or shop, follow the instructions that come with the packet.

Dosage and strength

Cetirizine comes as tablets and capsules (10mg) and as a liquid medicine (labelled either 5mg/5ml or 1mg/1ml).

The usual dose for adults is 10mg once a day.

Doses are usually lower for people with kidney problems.

Children

• For children between 6 to 11 years of age, the usual dose is 5mg, twice a day. Try to leave 10 to 12 hours between doses. So, one first thing in the morning, and one before bedtime.
• For children between 2 to 5 years of age, the dose is 2.5mg, twice a day.
• For children between 1 to 2 years of age, your doctor will use their weight or age to work out the right dose.

How to take it

You can take cetirizine with or without food, but always take the tablets or capsules with a drink of water, milk or squash. Swallow them whole. Do not chew them.

Cetirizine liquid may be easier for children to take than tablets. The liquid medicine will come with a plastic syringe or spoon to give the right dose. If you do not have a syringe or spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not measure out the right amount.

When to take it

You may only need to take cetirizine on a day you have symptoms for example, if you have been in contact with something that has triggered your allergy, like animal hair.

Or you may need to take it regularly to prevent symptoms for example, to stop hay fever during spring and summer.

What if I forget to take it?

Take your forgotten dose as soon as you remember, unless it's nearly time for your next dose. In this case, skip the missed dose and take your next dose at the usual time.

Do not take 2 doses to make up for a forgotten dose.

If you forget to give a dose to a child who is taking cetirizine twice a day, you can give the missed dose if it's within 4 hours of when they should have had it.

If you remember more than 4 hours after, do not give the missed dose. Instead, wait until the next dose and carry on as normal.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Cetirizine is generally very safe. Taking more than the usual dose is unlikely to harm you or your child.

If you take an extra dose, you might get some of the common side effects. If this happens or you're concerned, contact your doctor.

Allergy medications: Know your options

Allergy medications: Know your options

Several types of medications are used to treat allergy symptoms. Here's more information.

By Mayo Clinic Staff

Allergy medications are available as pills, liquids, inhalers, nasal sprays, eyedrops, skin creams and shots (injections). Some are available over-the-counter; others are available by prescription only. Here's a summary of the types of allergy medications and why they're used.

Antihistamines

Antihistamines block histamine, a symptom-causing chemical released by your immune system during an allergic reaction.

Pills and liquids

Oral antihistamines are available over-the-counter and by prescription. They ease a runny nose, itchy or watery eyes, hives, swelling, and other signs or symptoms of allergies. Because some of these drugs can make you feel drowsy and tired, take them with caution when you need to drive or do other activities that require alertness.

Antihistamines that tend to cause drowsiness include:

• Diphenhydramine
• Chlorpheniramine

These antihistamines are much less likely to cause drowsiness:

• Cetirizine (Zyrtec, Zyrtec Allergy)
• Desloratadine (Clarinex)
• Fexofenadine (Allegra, Allegra Allergy)
• Levocetirizine (Xyzal, Xyzal Allergy)
• Loratadine (Alavert, Claritin)

Nasal sprays

Antihistamine nasal sprays help relieve sneezing, itchy or runny nose, sinus congestion, and postnasal drip. Side effects of antihistamine nasal sprays might include a bitter taste, drowsiness or feeling tired. Prescription antihistamine nasal sprays include:

• Azelastine (Astelin, Astepro)
• Olopatadine (Patanase)

Eyedrops

Antihistamine eyedrops, available over-the-counter or by prescription, can ease itchy, red, swollen eyes. These drops might have a combination of antihistamines and other medicines.

Side effects might include headache and dry eyes. If antihistamine drops sting or burn, try keeping them in the refrigerator or using refrigerated artificial-tear drops before you use them. Examples include:

• Ketotifen (Alaway, Zaditor)
• Olopatadine (Pataday, Patanol, Pazeo)
• Pheniramine and naphazoline (Visine, Opcon-A, others)

Decongestants

Decongestants are used for quick, temporary relief of nasal and sinus congestion. They can cause trouble sleeping, headache, increased blood pressure and irritability. They're not recommended for people with high blood pressure, cardiovascular disease, glaucoma or hyperthyroidism.

Pills and liquids

Oral decongestants relieve nasal and sinus congestion caused by hay fever (allergic rhinitis). Many decongestants, such as pseudoephedrine (Sudafed), are available over-the-counter.

A number of oral allergy medications contain a decongestant and an antihistamine. Examples include:

• Cetirizine and pseudoephedrine (Zyrtec-D 12 Hour)
• Desloratadine and pseudoephedrine (Clarinex-D)
• Fexofenadine and pseudoephedrine (Allegra-D)
• Loratadine and pseudoephedrine (Claritin-D)

Nasal sprays and drops

Nasal decongestant sprays and drops relieve nasal and sinus congestion if used only for a short time. Repeated use of these drugs for more than three consecutive days may result in a cycle where congestion recurs or gets worse. Examples include:

• Oxymetazoline (Afrin)
• Tetrahydrozoline (Tyzine)

Corticosteroids

Corticosteroids relieve symptoms by suppressing allergy-related inflammation.

Nasal sprays

Corticosteroid sprays prevent and relieve stuffiness, sneezing and runny nose. Side effects can include an unpleasant taste, nasal irritation and nosebleeds. Examples include:

• Budesonide (Rhinocort)
• Fluticasone furoate (Flonase Sensimist)
• Fluticasone propionate (Flonase Allergy Relief)
• Mometasone (Nasonex)
• Triamcinolone (Nasacort Allergy 24 Hour)

For people who are bothered by the feeling of liquid running down their throats or the unpleasant taste of these sprays, there are two aerosol formulas:

• Beclomethasone (Qnasl)
• Ciclesonide (Zetonna)

Inhalers

Inhaled corticosteroids are often used daily as part of treatment for asthma caused or complicated by reactions to airborne allergy triggers (allergens). Side effects are generally minor and can include mouth and throat irritation and oral yeast infections.

Some inhalers combine corticosteroids with long-acting bronchodilators. Prescription inhalers include:

• Beclomethasone (Qvar Redihaler)
• Budesonide (Pulmicort Flexhaler)
• Ciclesonide (Alvesco)
• Fluticasone (Flovent)
• Mometasone (Asmanex Twisthaler)

Eyedrops

Corticosteroid eyedrops are used to relieve persistent itchy, red or watery eyes when other interventions aren't effective. A physician specializing in eye disorders (ophthalmologist) usually monitors the use of these drops because of the risk of problems, such as cataracts, glaucoma and infection. Examples include:

• Fluorometholone (Flarex, FML)
• Loteprednol (Alrex, Lotemax)
• Prednisolone (Omnipred, Pred Forte, others)

Pills and liquids

Oral corticosteroids are used to treat severe symptoms caused by all types of allergic reactions. Long-term use can cause cataracts, osteoporosis, muscle weakness, stomach ulcers, increased blood sugar (glucose) and delayed growth in children. Oral corticosteroids can also worsen high blood pressure.

Prescription oral corticosteroids include:

• Prednisolone (Prelone)
• Prednisone (Prednisone Intensol, Rayos)
• Methylprednisolone (Medrol)

Skin creams

Corticosteroid creams relieve allergic skin reactions such as itching, redness or scaling. Some low-potency corticosteroid creams are available without a prescription, but talk to your doctor before using these drugs for more than a few weeks.

Side effects can include skin discoloration and irritation. Long-term use, especially of stronger prescription corticosteroids, can cause thinning of the skin and abnormal hormone levels. Examples include:

• Betamethasone (Dermabet, Diprolene, others)
• Desonide (Desonate, DesOwen)
• Hydrocortisone (Locoid, Micort-HC, others)
• Mometasone (Elocon)
• Triamcinolone

Mast cell stabilizers

Mast cell stabilizers block the release of chemicals in the immune system that contribute to allergic reactions. These drugs are generally safe but usually need to be used for several days to produce the full effect. They're usually used when antihistamines are not working or not well-tolerated.

Nasal spray

Over-the-counter nasal sprays include cromolyn (Nasalcrom).

Eyedrops

Prescription eyedrops include the following:

• Cromolyn (Crolom)
• Lodoxamide (Alomide)
• Nedocromil (Alocril)

Leukotriene inhibitors

A leukotriene inhibitor is a prescription medication that blocks symptom-causing chemicals called leukotrienes. This oral medication relieves allergy signs and symptoms including nasal congestion, runny nose and sneezing. Only one type of this drug, montelukast (Singulair), is approved for treating hay fever.

In some people, leukotriene inhibitors can cause psychological symptoms such as anxiety, depression, strange dreams, trouble sleeping, and suicidal thinking or behavior.

Allergen immunotherapy

Immunotherapy is carefully timed and gradually increased exposure to allergens, particularly those that are difficult to avoid, such as pollens, dust mites and molds. The goal is to train the body's immune system not to react to these allergens.

Immunotherapy might be used when other treatments aren't effective or tolerated. It is also helpful in reducing asthma symptoms in some patients.

Shots

Immunotherapy may be given as a series of injections, usually one or two times a week. The dose may be increased weekly or every two weeks based on the patient's tolerance. Injections of the maximum tolerated dose may then be given every two to four weeks year round.

Side effects might include irritation at the injection site and allergy symptoms such as sneezing, congestion or hives. Rarely, allergy shots can cause anaphylaxis, a sudden life-threatening reaction that causes swelling in the throat, difficulty breathing, and other signs and symptoms.

Sublingual immunotherapy (SLIT)

With this type of immunotherapy, you place an allergen-based tablet under your tongue (sublingual) and allow it to be absorbed. This treatment has been shown to reduce runny nose, congestion, eye irritation and other symptoms associated with hay fever. It also improves asthma symptoms.

One SLIT tablet contains dust mites (Odactra). Several SLIT tablets contain extracts from pollens of different types of grass, including the following:

• Short ragweed (Ragwitek)
• Sweet vernal, orchard, perennial rye, Timothy and Kentucky blue grass (Oralair)
• Timothy grass (Grastek)

Biological medications

Some medications target a specific reaction in the immune system and try to prevent it from happening. These medications are given as injections. They include dupilumab (Dupixent) to treat allergic skin reactions and omalizumab (Xolair) to treat asthma or hives when other medications don't help.

Side effects of biological medications may include redness, itchiness, or irritation of the eyes and irritation at the injection site.

Emergency epinephrine shots

Epinephrine shots are used to treat anaphylaxis, a sudden, life-threatening reaction. The drug is administered with a self-injecting syringe and needle device (auto-injector). You might need to carry two auto-injectors if there's a chance you could have a severe allergic reaction to a certain food, such as peanuts, or if you're allergic to bee or wasp venom.

A second injection is sometimes needed. As a result, it's important to call 911 or get immediate emergency medical care.

A health care professional will train you on how to use an epinephrine auto-injector. It's important to get the type that your doctor prescribes, as the method for injection may differ slightly for each brand. Also, be sure to replace your emergency epinephrine before the expiration date.

Examples of these medications include:

• Adrenaclick
• Auvi-Q
• EpiPen
• EpiPen Jr

Get your doctor's advice

Work with your doctor to choose the most effective allergy medications and avoid problems. Even over-the-counter allergy medications have side effects, and some allergy medications can cause problems when combined with other medications.

It's especially important to talk to your doctor about taking allergy medications in the following circumstances:

• You're pregnant or breast-feeding.
• You have a chronic health condition, such as diabetes, glaucoma, osteoporosis or high blood pressure.
• You're taking other medications, including herbal supplements.
• You're treating allergies in a child. Children need different doses of medication or different medications from adults.
• You're treating allergies in an older adult. Some allergy medications can cause confusion, urinary tract symptoms or other side effects in older adults.
• You're already taking an allergy medication that isn't working. Bring the medication with you in its original bottle or package when you see your doctor.

Keep track of your symptoms, when you use your medications and how much you use. This will help your doctor figure out what works best. You might need to try a few medications to determine which are most effective and have the least bothersome side effects for you.

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March 05, 2022Show references

1. Allergy meds could affect your driving. U.S. Food and Drug Administration. https://www.fda.gov/consumers/consumer-updates/allergy-meds-could-affect-your-driving. Accessed Feb. 8, 2020.
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9. Sublingual immunotherapy (SLIT). American College of Allergy, Asthma & Immunology. https://acaai.org/allergies/allergy-treatment/allergy-immunotherapy/sublingual-immunotherapy-slit. Accessed Feb. 29, 2020.

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