Allergy medicine

There are many different types of allergies including: 

• Food allergies — common food allergies include cow’s milk, shellfish, peanuts, and eggs 
• Hay fever (allergic rhinitis) — an allergy to pollen that is usually worse in the summer months 
• Atopic asthma — a type of asthma that is triggered by allergens such as house dust mites, animal dander, pollen, and mould 
• Eczema (atopic dermatitis) — a skin condition that is common in children and may be triggered by contact with allergens such as soaps and detergents as well as other factors including stress and the weather  
• Paediatric (childhood) allergies —allergies in children are common and many children outgrow their allergies as they get older 
• Drug allergies — drugs that commonly trigger allergies include antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs) and aspirin 
• Insect bites and stings — insect stings such as bee and wasp stings, or bites from mosquitoes, midges or ticks can be serious and lead to a life-threatening allergic reaction (anaphylaxis) 

Allergy symptoms vary in type and severity depending on what you are allergic to and how severe your allergic reaction is. Common allergy symptoms include: 

• Runny or blocked nose 
• Itchy, watery eyes 
• Pain, pressure or tenderness around your cheeks, eyes, or forehead
• Coughing
• Sneezing
• Wheezing (noisy breathing)
• Shortness of breath
• Raised, red, itchy rash (hives)
• Nausea 
• Vomiting 
• Diarrhoea
• Swelling of the eyes, lips, mouth, or throat

Anaphylaxis 

Anaphylaxis is a severe, life-threatening allergic reaction that needs immediate treatment. Symptoms can come on very quickly after exposure to an allergen such as food, medication, or an insect sting. 

Symptoms of anaphylaxis include: 

• Difficulty breathing or rapid breathing 
• Difficulty swallowing, or speaking 
• Swelling of your throat and tongue
• Wheezing
• Confusion 
• Fatigue 
• Feeling faint or dizzy
• Fainting
• Blue, grey, or pale skin, lips, or tongue 
• Skin that feels cold to the touch
• In some cases, an itchy, raised, red rash (hives)

If you have had anaphylaxis before, you will have been given an adrenaline auto-injector. Use the auto-injector as soon as you can and call 999 for an ambulance. If this is your first anaphylactic reaction call an ambulance or get to your nearest A&E department as soon as possible. 

At your first consultation, you will be seen by an allergy specialist which may be a consultant specialising in allergies affecting the skin (a dermatologist), an Ear, Nose and Throat (ENT) specialist, or an allergist (a doctor specialising in allergies and immunology).  

Your consultant will ask you about your symptoms, general health, medical history, and any medications you are taking. They will perform a physical examination and ask you some questions about: 

• Your medical history including any other allergies, asthma, eczema, or hay fever 
• Your family history and whether you have any close family members with allergies, asthma, eczema, or hay fever
• Your symptoms and what triggers them 
• Any previous treatment you have tried for your allergy and how successful it was

Your consultant may refer you for allergy testing to confirm what you are allergic to and how severe your allergy is.

How is a diagnosis made?

Your consultant will make a diagnosis based on your symptoms, medical history, physical examination, and test results.

Why is this first consultation so important?

At Circle Health Group, your first appointment is very important as it’s where you first meet your consultant, the doctor responsible for your care. Your consultant will spend time getting to know you, asking about your symptoms, and ordering tests to ensure an accurate diagnosis. Your first appointment is also an opportunity for you to discuss any questions or concerns you may have about your diagnosis and treatment.

At the end of your appointment, your consultant will discuss possible treatment options, and decide on the best option for you based on your diagnosis, general health, lifestyle, and expectations for treatment. 

Common allergy medicines include antihistamines, decongestants, and corticosteroids. Your consultant will recommend a medication, or combination of medications for you depending on your symptoms, diagnosis, lifestyle, and which allergy medicines you have tried before. 

Antihistamines 

Antihistamines work by blocking the effects of histamine, the chemical your body releases when you experience an allergic reaction. They are not a cure for allergies but can help to relieve allergy symptoms when you take them. 

There are two main types of antihistamines, older antihistamines, known as first-generation antihistamines or drowsy antihistamines make you feel sleepy or drowsy after taking them. More recent second-generation antihistamines, or non-drowsy antihistamines are less likely to make you feel sleepy. 

Some common first-generation antihistamines include: 

• Cinnarizine
• Promethazine
• Chlorphenamine
• Hydroxyzine
• Diphenhydramine

Some common second-generation antihistamines include:  

• Fexofenadine
• Loratadine
• Acrivastine 
• Cetirizine

Many antihistamines can be bought over the counter, but you will need a prescription for stronger ones. Antihistamines are available as tablets, nasal sprays, capsules, liquids, eye drops, topical gels, and lotions. 

How long do antihistamines take to work? 

Most antihistamines start working within half an hour of taking them and are at their most effective after between one and two hours. Some antihistamines are short-acting and last for around four to six hours, while longer-lasting varieties can relieve allergy symptoms for twelve or even twenty-four hours. Check with your consultant or pharmacist how often you need to take your antihistamine and read the patient information leaflet carefully before starting your medication. 

When should I take antihistamines? 

Your consultant will tell you how to take your antihistamines correctly. You may be advised to take your medication before coming into contact with your allergy trigger to prevent symptoms from starting, or once symptoms have started to provide relief. If you have a condition such as hay fever, where you are likely to be exposed to your allergy trigger every day, your consultant may advise you to take antihistamines regularly as a preventative treatment. 

Which antihistamine should I take? 

Your consultant will recommend or prescribe an antihistamine depending on your symptoms, the type of allergy you have, and your lifestyle. You may need to try a few different antihistamines before finding one that works best for you. Second-generation (non-drowsy) antihistamines are normally preferable as they usually allow you to carry on with day-to-day activities such as working and driving. If your allergy is making it difficult for you to sleep, your consultant may recommend an antihistamine that makes you drowsy to help you fall asleep. 

Decongestants 

Decongestants are a type of medicine that can provide short-term relief from nasal congestion (a blocked or stuffy nose). They can help with allergies like hay fever where nasal congestion is a symptom. Decongestants work by reducing swelling in the blood vessels in your nose, which helps to open your airways and relieve congestion. Most decongestants are available over the counter as tablets, nasal sprays, drops, liquids, or dissolvable powders. They may be sold alone or in a combined tablet that also contains a painkiller and/or an antihistamine. 

Some common decongestants include: 

• Ephedrine
• Oxymetazoline
• Xylometazoline
• Phenylephrine
• Pseudoephedrine
• Ipratropium bromide

How long do decongestants take to work?

How long your decongestant takes to work depends on the type and form of the decongestant you are taking. Nasal drops and sprays usually work very quickly after use. Pseudoephedrine normally starts to work after around 15 minutes, and you should start to feel better after between 30 and 60 minutes. 

When should I take decongestants? 

Take decongestants when you have symptoms of nasal congestion. How often you need to take them depends on your symptoms and the type of decongestant you are using. Most decongestants can be taken one to four times a day. Check with your consultant how often you can take your decongestant. Some decongestants such as pseudoephedrine have a stimulant effect and may keep you awake, so it may be best to avoid taking them before bed. Decongestant nasal sprays are less likely to have this effect. 

Which decongestant should I take?

There are a range of decongestants available over the counter from pharmacies. You may need to try a few before finding one that works best for you. Which decongestant is most suitable for you depends on your symptoms, medical history, lifestyle, and preference. If you are buying a decongestant over the counter, your pharmacist can recommend one. Your consultant may prescribe or recommend a decongestant that is best suited to your needs. 

Corticosteroids 

Corticosteroids, commonly known as steroids, are a type of medication that reduces inflammation in the body. They can be used to treat several allergic conditions including atopic asthma, hay fever, severe urticaria (hives), and eczema. Steroids come in several forms including tablets, nasal sprays, preventer inhalers, injections, and creams. Most steroids are only available with a prescription, but some steroid creams and nasal sprays can be bought over the counter. 

Some common corticosteroids include: 

• Prednisolone 
• Prednisone
• Dexamethasone 
• Beclometasone
• Budesonide
• Fluticasone
• Mometasone
• Cortisone 
• Hydrocortisone 
• Methylprednisolone

How long do corticosteroids take to work?

How long your medication takes to work depends on the type and form of the corticosteroid you are taking. 

• Steroid injections start to work immediately, and inflammation normally improves within a few days. The effect may last from a few weeks to several months
• Tablets such as prednisolone start to work within a few hours 
• Preventer inhalers like beclometasone start to work within 24 hours, but it may be several weeks before you see an improvement in your symptoms
• Steroid creams like hydrocortisone usually improve symptoms of eczema within a few days 
• Nasal sprays such as dexamethasone usually start to work in around a week, but it may take up to three weeks before your symptoms improve

When should I take corticosteroids? 

Corticosteroids may be prescribed for long or short-term use. How and when you need to take them depends on the type of corticosteroid you are using and the condition you are taking them for. Always take your medication exactly as your consultant tells you and ask your consultant or pharmacist if you have any questions. 

Which corticosteroid should I take?

Your consultant will prescribe the most suitable corticosteroid for you depending on your symptoms, diagnosis, and medical history. For over-the-counter steroid creams or nasal sprays, your pharmacist can help recommend one. 

Like all medications, allergy medicines can cause side effects in some people. Side effects are usually mild and improve within a few weeks. Your consultant will explain all the possible side effects of your medication before you start taking it to allow you to make an informed decision. You can reduce the risk of side effects by following your consultant’s instructions and taking your medication exactly as prescribed. Ask your consultant or pharmacist if you have any questions about your medication. 

If you experience unpleasant side effects, or if your side effects are getting worse or not going away, call your consultant for advice. 

Antihistamine side effects 

Possible side effects of antihistamines include: 

• Nausea 
• Vomiting 
• Headache
• Dizziness
• Dry mouth, nose, or throat
• Blurred vision
• Drowsiness — this is more common in first-generation antihistamines, but non-drowsy antihistamines may cause drowsiness in some people. Do not drive or operate machinery if you feel sleepy after taking antihistamines
• Reduced coordination and slower reaction times — more common in first-generation antihistamines
• Nervousness and irritability
• Difficulty peeing or not being able to pee
• Increased appetite 

Who should not take antihistamines? 

Antihistamines are safe for most people, but may not be recommended for people with certain conditions including: 

• Heart disease
• Liver disease
• Kidney disease 
• Epilepsy
• Enlarged prostate 
• Glaucoma 
• Breathing problems such as asthma, emphysema, or chronic bronchitis 
• High blood pressure 

Tell your consultant about any underlying health issues you have before taking antihistamines. 

Pregnancy and breastfeeding 

Some types of antihistamines such as loratadine are considered safe to take during pregnancy, or while breastfeeding. Tell your consultant if you are pregnant or breastfeeding before taking antihistamines. 

What can interact with antihistamines? 

Some medications and foods can interact with antihistamines which can change the way they work. Tell your consultant about any other medications, including over-the-counter medicines and supplements you are taking before taking antihistamines. 

Some foods and medications that can interact with antihistamines include: 

• Grapefruit/ grapefruit juice  — can lessen the effect of some antihistamines like fexofenadine 
• Alcohol — can increase drowsiness and should be avoided when taking antihistamines
• Medications —including some: 
  • Anti-depressants
  • Narcotics (strong painkillers)
  • Sleeping tablets
  • Indigestion remedies 
  • Seizure medications
  • Muscle relaxants 
  • Sedatives
  • Stomach ulcer medications

Decongestant side effects

Most people don’t experience side effects from decongestants and any side effects are usually mild and stop once you stop taking the medication. 

Decongestants are not usually recommended for more than seven days. The risk of side effects is higher if you take them for longer than this. 

Some possible side effects of decongestants include: 

• Drowsiness (look for non-drowsy decongestants)
• Irritation of the lining of your nose
• Headaches
• Agitation or restlessness 
• Nausea
• Vomiting 
• Dry mouth
• Rash

Who should not take decongestants? 

Most people can take decongestants safely, but they may not be suitable for everyone. Tell your consultant about any medical conditions or allergies you have before taking decongestants. Decongestants should not be taken by: 

• Children under the age of six
• Children between the ages of six and eleven for longer than five days 

Decongestants may not be suitable for you if you have: 

• Diabetes
• High blood pressure
• Hyperthyroidism (overactive thyroid gland) 
• An enlarged prostate
• Liver, kidney, heart, or circulation problems
• Glaucoma (increased pressure in the eye) 

Talk to your consultant if you have any of these conditions before taking decongestants. 

Pregnancy and breastfeeding 

If you are pregnant or breastfeeding, talk to your consultant before taking decongestants. 

What can interact with decongestants?

Some medications may change the way decongestants work which can increase or reduce the effect of your other medicines or cause dangerous side effects. Tell your consultant about any medications, including over-the-counter medicines and supplements before taking decongestants. Some all-in-one medications that contain a decongestant may contain other drugs like painkillers or antihistamines, so make sure you know what’s in your medication and be careful not to take too much without realising. 

Don’t take decongestants if you take a type of antidepressant called a monoamine oxidase inhibitor (MAOI). Taking these medications at the same time can cause a dangerous increase in blood pressure. 

Pregnancy and breastfeeding 

It's not clear whether decongestants are safe to take if you are pregnant or breastfeeding. Only use decongestants if they are prescribed or recommended by your consultant and tell them you are pregnant or breastfeeding before starting your medication.  

Corticosteroid side effects 

Corticosteroids can cause side effects, particularly when taken for a long period of time. Some of these side effects can be serious. Potential side effects of corticosteroids vary depending on the type of medication you are taking, but may include:

• Increased appetite
• Weight gain 
• Mood disorders such as depression 
• Insomnia (difficulty sleeping)
• Acne
• Increased risk of infection
• Bruising
• High blood pressure
• High blood sugar 
• Osteoporosis
• Cataracts
• Glaucoma
• Liver damage
• Adrenal fatigue 
• Thinning of the skin 

What can interact with corticosteroids? 

Corticosteroids can interact with certain foods or medications which can change the way they work. Tell your consultant about any medications including over-the-counter medicines and supplements you are taking. Some corticosteroids should not be taken with food as interactions may occur. Drinking alcohol and smoking tobacco can also interact with corticosteroids. Talk to your consultant about food, alcohol, and tobacco consumption before starting your medication. 

Some medications that can interact with corticosteroids include: 

• Anticoagulants (blood thinners)
• Some blood pressure medications
• Some drugs used to treat epilepsy 
• Some drugs used to treat diabetes 
• Antifungal drugs
• Bronchodilators (such as salbutamol) 
• Diuretics (water tablets) 

Who should not take corticosteroids? 

Corticosteroids may not be suitable for everyone. Tell your consultant about any medical conditions and allergies you have before taking corticosteroids.

Corticosteroids may not be suitable for you if you have: 

• Diabetes
• Epilepsy
• HIV/AIDS
• Any kind of infection 
• Depression
• Obesity
• A history of substance abuse 
• Glaucoma 
• Cataracts
• Stomach ulcers
• High blood pressure
• Heart, liver, kidney, or thyroid disease 

Pregnancy and breastfeeding 

Some corticosteroids, such as prednisolone are considered safe to take during pregnancy and while breastfeeding. Tell your consultant if you are pregnant or breastfeeding before taking corticosteroids. 

At Circle Health Group, we have the experience and expertise to ensure the best possible care and outcome for our patients. As a patient with Circle Health Group, you can expect the highest standards of care including: 

• Flexible appointment times and locations that are convenient for you
• The freedom to choose which hospital and consultant suit your needs
• Personalised, consultant-led treatment plans tailored to your individual needs
• Comfortable and safe private facilities maintained by expert multidisciplinary teams
• Private ensuite rooms as standard
• A range of delicious healthy meals
• Affordable, fixed-price packages with aftercare included
• Flexible payment options to help you spread the cost of your care

If you would like to see a consultant or learn more about allergy treatment, book your appointment online today or call a member of our team directly on 0808 189 5499.

Content reviewed by Circle in-house team in May 2024. Next review due May 2027.

Antihistamines NHS
Allergy medications: Know your options Mayo Clinic 
Allergies NHS 
Allergen Immunotherapy: Current and Future Trends   PubMed 
Types of Allergies Allergy UK