Atopic dermatitis is an inflammatory, IgE-mediated skin disease characterized by intense pruritus, xerosis, and scaly, licheniform rash with a characteristic anatomical distribution. Therapy is directed at avoidance of inciting stimuli, moisture retention, emollients, antipruritics, and topical corticosteroids.
One report of a placebo-controlled, randomized, crossover study suggests that topical cromolyn may potentially benefit patients for whom the above therapeutic modalities have failed. Cromolyn prepared in an emollient base was applied to the skin of children and adolescents with moderate to severe atopic dermatitis. All subjects concomitantly applied a mid-potency topical steroid. Objective severity decreased significantly in the cromolyn-steroid group compared to the group treated with steroid alone. The study authors posit an additive anti-inflammatory effect based on the different mechanisms of action employed by corticosteroids and cromolyn.
Nedocromil may inhibit sensory nerve activation to reduce neurogenic itch and flare from histamine but does not modulate wheal diameter. It has not yet been evaluated clinically as a topical preparation.
Other reports have proposed that intranasal cromolyn or nedocromil (not commercially available in the United States as an intranasal preparation) may benefit the common cold. The causative viruses or atypical bacteria may produce a variety of inflammatory mediators, including histamine, cytokines, leukotrienes, and nitric oxide. Compared to placebo, both cromolyn and nedocromil provide a swifter resolution and reduced severity of symptoms in nonallergic subjects. Both drugs also reduce symptoms of virus-induced asthma exacerbations.
Systemic mastocytosis, a disease characterized by mast cell proliferation in multiple organ systems, usually features urticaria pigmentosa (brownish macules that transform into wheals upon stroking them) and recurrent episodes of flushing, tachycardia, pruritus, headache, syncope, abdominal pain, or diarrhea. Because it inhibits mast cell degranulation, orally administered cromolyn has some efficacy in mastocytosis, particularly for symptoms involving the gastrointestinal tract. However, cromolyn does not reduce plasma or urinary histamine levels in patients with mastocytosis.
Similarly, oral cromolyn has been employed as an alternative to an elimination diet in non-life-threatening food allergy, in irritable bowel syndrome, and atopic dermatitis where allergic sensitization to specific foods has been identified.
One group has reported that cromolyn has an antisickling effect in patients with sickle cell disease and concomitant allergic disease. The researchers postulate that the decrease in sickle cells may be a result of inhibitory effects of cromolyn on the calcium-activated potassium Gardos channel, which influences erythrocyte dehydration. Of the studied 18 patients with sickle cell disease, 10 were also taking hydroxyurea, and the report does not mention the duration of treatment or if the hydroxyurea dosage was altered. The clinical effect of reduced sickling activity was also not discussed. Clinical relevance therefore is uncertain.
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