Specific desensitization in 'aspirin-sensitive' urticaria; plasma prostaglandin levels and clinical manifestations

Hypersensitivity reactions to food additives

Only seldom have food additives been shown to cause true allergic (immunological) reactions. Adverse effects due to various pharmacological or other mechanisms are much more common. The individual tolerance may be decreased for one reason or another, and may fluctuate from time to time. Many patients suffering from food additive reactions have atopic constitutions and such clinical symptoms as flexural dermatitis, rhinitis and asthma. The most important skin symptoms caused by food additives are urticaria, angioneurotic edema, and contact urticaria. Azo dyes, benzoic acid and several other common food additives may aggravate or, more rarely, even cause urticaria. Spices are one of the most common causes of immunological contact urticaria. Non-immunological contact urticaria is produced by numerous spices, benzoic acid, sorbic acid, cinnamic acid, and many essential oils. Asthma and rhinitis are the main hypersensitivity symptoms in the respiratory tract, and azo dyes, benzoic acid, and sulfitic food additives are the most common causative agents. Systemic and respiratory reactions to food colorants and benzoates have been claimed to occur more frequently in acetylsalicylic acid- (ASA-)sensitive patients than in non-reactors. Hypersensitivity reactions in organs other than the skin and respiratory tract are rare or poorly documented. Psychological factors play an essential role in both food and food additive reactions.

Plasma esterase activity in patients with aspirin-sensitive asthma or urticaria

Plasma aspirin esterase activity and cholinesterase activity were reduced in patients with aspirin sensitive asthma and aspirin sensitive urticaria compared to asthmatic and dermatological controls. Phenylacetate (non specific) esterase activities, were however unaltered in these patients. The reason for the lower activity is uncertain but it does not appear to be due to genetically determined lower cholinesterase or due to the avoidance of aspirin by sensitive patients. A low aspirin esterase activity may be a contributory factor in precipitating these aspirin sensitive reactions.

Serum 13-14-diOH-15-keto-prostaglandin F2 alpha and airway response to meclofenamate and metaproterenol in relation to the menstrual cycle

In order to evaluate whether adverse reactions to a nonsteroidal antiinflammatory agent (NSAIA) were related to variations in prostaglandin levels during the menstrual cycle, we measured 13-14-diOH-15-keto-prostaglandin F2 alpha in serum and the effect on airways of a single dose of 100 mg oral meclofenamate and 1.5 mg inhaled metaproterenol during the early (follicular phase) and late (luteal phase) menstrual cycle. Among 24 women with premenstrual asthma (PMA), four women with regular asthma (REA), and four healthy women, the 13-14-diOH-15-keto-PGF2 alpha averaged 140.9 +/- 68.4 pg/0.1 ml during the follicular phase but only 14.4 +/- 2.2 pg/0.1 ml during the luteal phase (p less than 0.0001). Acute asthma reactions to the meclofenamate occurred during the follicular phase in six women with PMA but were never observed during the luteal phase (p = 0.016). These reactions occurred preferentially in patients on corticosteroids (p = 0.004). Conversely, one patient with PMA had 18% improvement in FEV1 with meclofenamate during the luteal phase. A placebo-controlled, double-blind evaluation of the healthy women and the women with REA revealed a trend toward improvement in FEV1 during the luteal phase (0.15 less than p less than 0.10) but no change during the follicular phase. The effect of metaproterenol did not vary with the menstrual cycle, and there was no interaction between the effects of meclofenamate and those of metaproterenol. It appears that meclofenamate causes adverse effects on pulmonary function in asthmatic women primarily during the follicular phase of the menstrual cycle. This effect is associated with corticosteroid treatment and may be related to monthly variation in serum 13-14-diOH-15-keto-PGF2 alpha.

Mediators, airway responsiveness, and asthma

There appears to be a close interrelationship among airway responsiveness to mediators and to natural stimuli, the presence and severity of asthma, and endogenous mediator release in the airways. Histamine and methacholine have been most commonly used to measure airway responsiveness. Airway responsiveness to the two drugs is increased in patients with current symptoms of asthma, and the degree of increase relates closely to the degree of variable airflow obstruction and the therapy to control symptoms. The degree of airway responsiveness to histamine also correlates closely with the degree of responsiveness to methacholine and less closely with responsiveness to PGF2 alpha and to natural stimuli such as exercise and allergens. The less close correlations with responsiveness to exercise and allergens is probably because of variations in the ease and type of endogenous mediator release in the airways by these stimuli. Endogenous mediator release from a number of stimuli including allergens and ozone causes inflammation in the airways, asthma, and airway hyperresponsiveness. These various interrelationships indicate that the treatment of asthma should be directed to reduce airway responsiveness, prevent mediator release, and prevent or reverse inflammation.

Effect of aspirin on nasal resistance to airflow

The effect of aspirin on nasal resistance to airflow was investigated by rhinomanometry in 25 healthy subjects before and after ingestion of aspirin or vitamin C in a double blind crossover trial. Aspirin caused a significant increase in nasal resistance compared with vitamin C. The effect of aspirin may be due to its inhibition of the synthesis of prostaglandins.

Food intolerance

Food intolerant symptoms can have various causes, including enzyme deficiencies (of lactase or aldehyde dehydrogenase) and pharmacological effects (e.g., caffeine, salicylates). The irritable bowel syndrome can also be associated with intolerance to specific foods in some cases, but the mechanism is unclear. Immunological causes are less common but may explain the small bowel mucosal changes associated with gluten enteropathy, as well as the childhood enteropathy provoked by cow's milk or, rarely, by other foods. Food allergy of the more immediate and classical type is associated with reactions both within and outside the gastrointestinal tract. Where these include urticaria, asthma and eczema, immunoglobulin E antibodies are often demonstrable by skin or radioallergosorbent tests, but pseudo-allergic reactions can produce a similar clinical picture. Diagnosis of food intolerance depends on withdrawing the food concerned and assessing the response to a blind challenge. Objective ways of detecting subclinical reactions are also useful, including the detection of a mediator response involving prostaglandins, histamine or serotonin.

Effect of aspirin in "aspirin sensitive" patients

Eighteen patients with a history of urticaria or asthma, or both, induced by aspirin were studied before and after provocation of symptoms with aspirin. The plasma prostaglandin F2 alpha concentration, which was characteristically raised before challenge, fell significantly at the time of adverse reactions. Repeated administration of aspirin up to a dose of 650 mg daily induced tolerance in most of the patients, and several developed bronchodilator responses to aspirin. Although median total IgE concentrations may be raised in patients with aspirin sensitivity, it appears likely that pharmacological rather than immunological mechanisms are chiefly responsible for the phenomena of aspirin sensitivity and desensitisation.