The term “food intolerance” is used to denote reactions to food which do not involve a known immune mechanism.

Aspirin and Salicylate

1. Aspirin

Intolerance to aspirin (acetyl salicylic acid) is well described.  Other forms of salicylates (Table 1), and particularly sodium salicylate, occur naturally in nature in a wide variety of plants and foods (Table 2 and 3).

The deleterious effects of aspirin are well documented (Table 4) and removal of aspirin from an aspirin-sensitive individual may result in amelioration of symptoms.  However the benefit of a salicylate-free diet remains a contentious issue.  Dahl showed that aspirin-sensitive patients are not affected by sodium salicylate in that aspirin-sensitive asthmatics with dramatic peak flow changes following a challenge of aspirin in doses up to 200 mg, demonstrated no changes to a sodium salicylate challenge with doses up to 2,000 mg. (Ref.1).

A brief overview of the more common reactions follows:

i.) Asthma

Adult asthmatics, particularly in their 3^rd or 4^th decade, are more prone to develop a salicylate intolerance than children.  Initially, an intense rhinitis with very watery and intermittent rhinorrhoea is experienced, and this is followed after a few months by chonic nasal congestion.  Nasal polyposis may be found on examination in these patients.  Asthma and occasionally conjunctivitis develops later on.  Symptoms occur up to an hour after ingestion of aspirin.  The asthma precipitated may be life threatening.  Asthma and nasal polyposis associated with salicylates follows a protracted course even if aspirin is avoided thereafter. (Ref. 2).  Paradoxically aspirin has been reported to relieve asthma in some patients.

Children with asthma may also be affected by aspirin.

ii.) Chronic Urticaria

Aspirin has been found to be a trigger factor in a percentage of adult patients with chronic urticaria.  Children are less affected.  There appears to be a different mechanism in asthma and urticaria, and patients rarely have both tiggered by aspirin. (Ref. 3).

iii.) Nasal Polyposis

Rhinorrhoea and the development of nasal polyposis can be provoked by aspirin, but more often in adults than in children.

iv.) Laryngeal Oedema

Two non-asthmatic adults were anecdotally reported to have developed hoarseness and laryngeal oedema. (Ref. 4).

v.) Hyperactivity

Although many authors suggest that salicylates result in behaviour problems in children there is no objective evidence from double blind placebo controlled trials to support this.

2. Salicylates

Various symptoms, including hyperactivity, have been attributed to an intolerance to salicylates.  Many foods, vegetables, fruits and even tap water, have been shown to have varying degrees of salicylate content.  Spices in particular have a high content.  Although some authors have suggested that salicylates in food affect aspirin sensitive individuals, there is no evidence from double blind studies to confirm this.

3. Cross-reactivity

There are many other analgesics that show crossreactivity with salicylates resulting in bronchospasm in aspirin-sensitive asthmatics.  (Table 5).

Intravenous hydrocortisone may worsen asthma in some aspirin-sensitive adults.  Methylprednisolone, dexamethasone and betamethasone appear to be safe in these patients.

Some studies have shown that aspirin sensitive patients are also sensitive to tartrazine and other azo colour dyes.  This is contradicted by other studies and thus remains inconclusive. (Ref. 5).

4. Diagnosis and Management

Salicylate sensitivity can only be proven by careful double blind placebo controlled challenges.  Other possible causes e.g. allergy, histamine, tyramine, sulphite sensitivity, etc. need exclusion.  Patients with proved salicylate senstivity should avoid other drugs which inhibit cyclo-oxygenase and which have not been proven safe by challenges.  A salicylate-free diet may benefit some patients but caution should be exercised before embarking a patient on a somewhat difficult diet.

Table 1:

Table 2: Foods containing salicylates

Table 3:

Table 4: Complications of Aspirin Ingestion

Table 5:
Complications of Aspirin Ingestion

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