Healthdirect Free Australian health advice you can count on.

Medical problem? Call 1800 022 222. If you need urgent medical help, call triple zero immediately

healthdirect Australia is a free service where you can talk to a nurse or doctor who can help you know what to do.

Woman using nasal spray

Woman using nasal spray
beginning of content


2-minute read

Allergies and allergic reactions are common. About a third of all Australians have allergies at some point in their lives. However, the symptoms of allergic reactions can generally be easily and effectively treated using a group of medicines called antihistamines.

Allergies and histamine

Your body can become sensitive to things around you, like foods, plants, animals and medicines. If you are allergic to something, it is called an allergen.

When the body is exposed to allergens it releases histamine, a chemical. Histamine makes you sneeze, makes your nose run, and makes you eyes and skin itch and swell up. In a way, it is trying to get you to sneeze out or scratch away the allergen.

Treating allergies and allergic reactions with antihistamines

Antihistamines are medicines that act by blocking the body's response to histamine. This reduces the severity of the reaction and eases the symptoms of allergy. Antihistamines are commonly used in the treatment of a number of conditions related to allergies and hypersensitivities like:

Some antihistamines can also be used to treat non-allergy-related conditions, such as motion sickness, insomnia and heartburn or indigestion.

Oral antihistamines can be used to treat all of the symptoms of an allergic reaction. Others come as eye drops or nasal sprays, for treating specific symptoms only. Some oral antihistamines may have a sedative effect, but others are non-sedating or non-drowsy.

Antihistamines don't treat very severe allergic reactions like anaphylaxis, as they work too slowly.

Side effects of antihistamines

Some people get side effects from oral antihistamines like:

  • tiredness
  • drowsiness
  • headache
  • dry mouth
  • upset stomach.

They usually don't last long.

If you use antihistamines you should be careful when operating machinery, such as driving a car. Even non-sedating antihistamines can make some people drowsy.

You should talk to a pharmacist or doctor before taking an antihistamine if you:

People with porphyria should talk to their doctor or pharmacist before taking antihistamines.

If you have any questions or concerns about antihistamines, please talk to your doctor or pharmacist.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: August 2017

Need more information?

These trusted information partners have more on this topic.

Top results

Australasian Society of Clinical Immunology and Allergy: tests, treatments and procedures clinicians and consumers should question

Recommendations from the Australasian Society of Clinical Immunology and Allergy (ASCIA) on the introduction of solids to infants, treatment of anaphylaxis, alternative allergy testing, allergen immunotherapy and food-specific IgE testing.

Read more on Choosing Wisely Australia website

Antihistamines and allergy | Australian Prescriber

There is now little role for sedating antihistamines in allergic conditions. Discover why they should be avoided.

Read more on Australian Prescriber website

Sinus and nasal problems -

Most sinus problems are due to allergy, infection, or a foreign substance inhaled up the nose. Find out what products are available for sinus and nasal problems.

Read more on myDr website

Hay fever treatments -

Antihistamines work fast and are good at treating mild symptoms of hay fever, such as sneezing and runny nose, whereas corticosteroid nasal sprays may take several days to work.

Read more on myDr website

Conjunctivitis: self-care -

A major cause of eye problems is allergic, bacterial or viral conjunctivitis (inflammation of the 'wet' surfaces of the eye). Find out what products are available for conjunctivitis.

Read more on myDr website

Food allergies in children and teenagers | Raising Children Network

If your child has food allergies, your child must avoid the foods shes allergic to. You need to know the symptoms and how to treat an allergic reaction.

Read more on website

Allergic and toxic reactions to seafood - Australasian Society of Clinical Immunology and Allergy (ASCIA)

Seafood allergy occurs most commonly where seafood is an important part of the diet, such as Asia and Scandinavia. It is more common in adults than children, usually remains a life-long problem and is most often restricted to only one seafood group.

Read more on ASCIA – Australasian Society of Clinical Immunology and Allergy website

Allergy and allergy tests | Sydney Children's Hospitals Network

What is allergy? Allergy is when a persons immune system reacts to a substance in the environment

Read more on Sydney Children's Hospitals Network website

Allergy Treatments - Australasian Society of Clinical Immunology and Allergy (ASCIA)

The Australasian Society of Clinical Immunology and Allergy (ASCIA) is the peak professional body of clinical immunology and allergy in Australia and New Zealand. ASCIA promotes and advances the study and knowledge of immune and allergic diseases, including asthma.

Read more on ASCIA – Australasian Society of Clinical Immunology and Allergy website

Allergy testing - Australasian Society of Clinical Immunology and Allergy (ASCIA)

Avoiding known allergic triggers is an important part of allergy and asthma management. Allergy testing (using Skin Prick tests or RAST blood tests) helps your doctor to confirm which allergens you are sensitive to, so that appropriate avoidance advice can be given.

Read more on ASCIA – Australasian Society of Clinical Immunology and Allergy website

Healthdirect 24hr 7 days a week hotline

24 hour health advice you can count on

1800 022 222

Government Accredited with over 140 information partners

We are a government-funded service, providing quality, approved health information and advice

Australian Government, health department logo ACT Government logo New South Wales government, health department logo Northen Territory Government logo Government of South Australia, health department logo Tasmanian government logo Government of Western Australia, health department logo