Histamine is the immune system protein credited with causing many of the symptoms of allergic rhinitis (nasal allergies) and other allergic reactions. While some allergy-fighting drugs work by blocking the action of histamine after it’s been released by mast cells, cromolyn sulfate is a so-called “mast cell stabilizer.” It helps prevent allergy symptoms by preventing mast cells from releasing histamine and other inflammatory chemicals in the first place. A mast cell is a type of immune system cell that initially responds to the presence of an allergen. Mast cells get the ball rolling, so to speak, by pouring histamine into the spaces between affected cells.

Cromolyn sodium (also called sodium cromoglycate, or cromoglicic acid) is used primarily to prevent allergy-induced asthma attacks. For general environmental allergies, cromolyn sodium is now considered second or third-line treatment, after nasal corticosteroids and antihistamines. Cromolyn sodium originally derived from the healing herb, ammi visnaga, used in Egypt since ancient times.

Among other uses, ammi visnaga traditionally controlled kidney stone pain. But its reputed ability to open airways intrigued early investigators, who eventually identified the plant’s active ingredient, cromolyn sodium. Although it’s known to prevent mast cells from launching the immune response that ultimately results in the unpleasant symptoms of allergies, it is uncertain exactly how this activity helps prevent asthma attacks.

Protection Against Allergy-Induced Asthma

For a time, cromolyn sodium represented a breakthrough of sorts in the prevention of allergy and/or exercise-induced asthma. Inhaled as a mist directly into the lungs, it is shown to significantly reduce the incidence of asthmatic episodes triggered by an allergic reaction.

In recent years, newer leukotriene inhibitor drugs have largely replaced medications featuring cromolyn sodium, due to their apparent safety and relative convenience. (Cromolyn sodium must be inhaled four times per day, while leukotriene inhibitors require only once-daily dosing.)

While the use of cromolyn sodium for the prevention of asthmatic episodes has declined, recently it has been used in a topical treatment for atopic dermatitis in children. Atopic dermatitis is an allergic inflammatory skin condition. When applied directly to the skin, cromolyn sodium has been shown to safely and effectively reduce the symptoms of this allergic condition. Cromolyn sodium isn’t significantly absorbed into the bloodstream when applied to the skin, which eliminates any concerns about systemic side effects. In other words, it doesn’t get into the bloodstream and circulate throughout the body. Its effects remain localized to the skin.

Recent studies have also shown that cromolyn sodium is useful for the treatment of allergic conjunctivitis. This is a condition of extreme eye redness and irritation that may result when allergens trigger inflammation in the lining of the eyelids. Although it resembles “pink eye,” allergic conjunctivitis is not contagious, since infectious agents do not cause it. A two percent ophthalmic solution was effective and safe for the short-term (four weeks) treatment of allergic conjunctivitis in a recent Taiwanese study.

Cromolyn sodium (specifically, disodium cromoglycate) is also regaining favor as an ingredient in medications for the prevention of exercise-induced asthma. A German study, for example, found that a single inhalation of a solution of disodium cromoglycate with reproterol before exercise provided significantly better prevention of exercise-induced asthma in test subjects than three days of pretreatment with an oral leukotriene inhibitor.

All in all cromolyn sodium is considered safe. For some people with a rare allergic condition, it may even be life-saving. Patients who take cromolyn by mouth are protected from a potentially lethal allergic reaction to wheat.