There are several types of medication available to manage the symptoms of an indoor allergy.
Medication
The three medications most widely used to treat an indoor allergy are:
Nasal decongestants
Nasal decongestants are usually available over-the-counter (OTC) in the form of a nasal spray. Only use a decongestant spray for short-term relief of your symptoms. Using the spray for longer than five to seven days may make your symptoms worse.
If you're taking a type of antidepressant known as a monoamine oxidase inhibitor (MAOI), do not use nasal decongestants. The combination of the two types of medication can cause serious side effects.
Antihistamines
Antihistamines are usually recommended as the initial treatment for a mild to moderate indoor allergy.
Antihistamines block the action of the chemical histamine, which the body releases when it thinks it is under attack from an allergen. Antihistamines can be taken as a tablet (oral), as nasal sprays or drops (topical intranasal).
Oral antihistamines are available over-the-counter (OTC) without prescription from your pharmacist. Antihistamine nasal sprays are only available with a prescription. Oral antihistamines are not suitable for children under two years of age and antihistamine nasal sprays are not suitable for children under five years of age.
In the past, antihistamines caused drowsiness, but new types were developed to avoid this side effect. However, around 10% of people are still affected by drowsiness.
If during the night your symptoms are particularly troublesome, you may prefer to take an older type of antihistamine because the side effect of drowsiness may help you to sleep better.
If you're taking antihistamines, see how you react to the medication before driving or operating heavy machinery. Antihistamines can cause drowsiness if you take them, especially if you drink alcohol.
You can take antihistamines if you are pregnant. However, to minimise any risk to your unborn child, it's recommended that you use a nasal spray rather than tablets. Older antihistamines, such as chlorphenamine (Piriton), loratidine and cetirizine, are preferred to newer medicines because there is more information available about their safety.
Corticosteroids
If your symptoms are frequent or persistent and you have a nasal blockage or nasal polyps, your GP may recommend that you use a nasal spray which contains corticosteroids (topical intranasal corticosteroids), either as a single treatment or in combination with antihistamines.
Corticosteroids block many of the functions of the immune system and also help to reduce inflammation. They take longer to work than antihistamines, but their effects last longer.
Side effects from inhaled corticosteroids are rare, but can include dryness and irritation of the nose, and nose bleeds.
If you need fast relief from your symptoms, you may be given a short-term course of oral antihistamines to take in combination with your corticosteroid nasal spray.
If your symptoms are severe and you're worried that they will have an impact on an important event, such as a driving test or exam, let your GP know. They may recommend taking a seven-day course of oral corticosteroids to control your symptoms.
The use of oral corticosteroids on a long-term basis isn't usually recommended. Long-term use can cause a range of side effects, such as weight gain and thinning of the skin.
Immunotherapy
Immunotherapy, sometimes known as hyposensitisation, involves gradually increasing your exposure to an allergen to make you less sensitive to it. It makes you less likely to react adversely to the allergen when you are exposed to it in the future.
Immunotherapy has proved particularly effective in treating people with an allergy to:
- cats
- dust mites
- fungal spores
- cockroaches
As immunotherapy involves a three- to five-year course of treatment, it is usually only recommended if your symptoms cannot be controlled with medication.
Immunotherapy may not be suitable for you if you have:
- severe asthma
- a weakened immune system, either as a result of a condition, such as HIV, or due to a side effect of a medical treatment, such as chemotherapy
- a serious health condition, such as heart disease or cancer
There are two main ways that immunotherapy is used:
- subcutaneous immunotherapy, where you are given regular injections of the allergen into your skin
- sublingual immunotherapy, where you are given a small capsule containing a sample of the allergen, which you dissolve under your tongue
Evidence suggests that subcutaneous immunotherapy may be more effective at relieving the symptoms of an allergy, although sublingual immunotherapy may be your preferred option if you don't like having regular injections.
It will usually take between six and twelve months before you notice an improvement in your symptoms.
There is a small risk of immunotherapy treatment triggering a serious allergic reaction known as anaphylaxis. Read more about the complications of indoor allergies.
