How Long Does It Take for an Allergy Medicine to Work?

Allergies are a reaction of the immune system to harmless substances. Allergies may cause nasal symptoms, hives, asthma or even anaphylaxis, a severe form of allergy that may be fatal. Most mild allergies can be controlled with simple, symptomatic treatments. The most important form of treatment, however, is for individuals to avoid the various foods, pollen, insect bites or other substances to which they may be allergic. Individuals with allergies should consult with their medical practitioner before starting treatment to ensure they are getting the best possible allergy control.

Antihistamines are the fastest-acting medication for seasonal allergies. (Image: Scharvik/iStock/Getty Images)


Antihistamines are used to treat a variety of allergic reactions. Histamine is an important chemical released during allergic reactions, and these medications work against this chemical. They are effective, for example, in the treatment of skin allergies and hay fever. Newer generation antihistamines offer allergy relief while causing minimal sleepiness. These medications typically begin to work within one and two hours. While asthma is also an allergic condition, antihistamines are not useful in the treatment of this disorder.


Steroids are also highly effective medications for treating allergic reactions. In contrast to antihistamines, however, steroids have a more gradual, but long-lasting, onset of action. Fluticasone, a steroid used as a nasal spray in the treatment of hay fever, takes a minimum of eight hours to be effective. However, the advantage of steroids is that they reduce the overall symptoms of allergy for extended periods of time. Steroids treat both nasal and eye symptoms. These medications also decrease the severity and the frequency of asthma attacks.

Cromolyn Sodium

Cromolyn sodium is an alternative medication for allergies. It is used for conditions such as asthma, allergy-induced pink eye and allergic nasal symptoms. While steroids are stronger and more effective to treat allergies, they may cause long-term complications such as weight gain, decreased immunity and weakened bones. Doctors may prescribe cromolyn as an alternative to a steroid. Unfortunately, the medication is slow to act; it may take up to four weeks for any improvement to occur with this medication.

Leukotriene Antagonists

Leukotriene antagonists are drugs such as montelukast and zafirlukast. These medications block the action of leukotrienes, chemicals which are released as a part of an allergic reaction. As with cromolyn, these medications may be tried as an alternative to steroids for asthma and for seasonal allergies. The medication is taken orally or as an inhaler, and often provide relief within 2 days of use.

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