Summary

A food and pharmaceutical ingredient, which may result in allergy symptoms in sensitised individuals.

Clinical Relevance

The first case of allergic reaction to psyllium seed was described as early as 1941. Since then, a great variety of allergic symptoms have been reported to the seed and dust of ispaghula, including asthma and/or rhinitis, pruritis of mouth and eyes, diarrhoea, vomiting, nausea, tachycardia, hypotension, cough, angioedema, abdominal cramping, wheezing, and urticaria. Acute bronchospasm associated with inhalation of psyllium hydrophilic mucilloid has also been described, as well as eosinophilia.

Three risk groups for hypersensitivity to psyllium have been described: consumers who consume psyllium laxatives; pharmaceutical workers who handle P. ovata seeds in the manufacture of laxatives; and health care professionals who prepare psyllium laxatives for their patients.

Anaphylaxis has been reported. There has been a case of immediate allergic reaction after ingestion of a dietary bar containing psyllium.

Cases of anaphylactic reaction have been reported in all risk groups after ingestion of laxative or breakfast cereals containing P. ovata seed. In most of those subjects, sensitisation occurred by inhalation of P. ovata seed dust in the workplace.

Anaphylaxis may occur following the first ingestion of psyllium, as described in a woman who experienced severe laryngeal oedema and fatal anaphylaxis following ingestion of a psyllium-containing product for the first time. She had previously worked as a nurse assistant preparing psyllium bulk laxatives for years. Serum-specific IgE was strongly positive for psyllium only, and negative for the remaining 21 ingredients of the ingested food product. Her serum tryptase level was elevated, indicating mast cell degranulation.

Psyllium hydrophilic mucilloid was added to breakfast cereals for cholesterol-lowering effects. A number of studies subsequently reported adverse reactions to the cereal. A 60-year-old woman with no prior history of psyllium ingestion developed anaphylactic symptoms after eating a psyllium-containing cereal. Her only previous exposure was dispensing a psyllium-containing laxative as a nurse. Skin-prick test was positive for psyllium. Sensitisation occurred by inhalation in the absence of symptoms (rhinitis, asthma) and her first hypersensitivity reaction was that of anaphylaxis by ingestion.

An anaphylactic reaction was reported to the psyllium-containing cereal Heartwise. In another study, of the 20 women evaluated with reported allergic reactions to Heartwise, all but 6 were nurses. Previous exposures to psyllium included ingestion or dispensing of psyllium-containing products. Symptoms developed shortly after small amounts of the cereal were ingested, and most commonly included moderate to severe wheezing, throat and chest tightness, and urticaria. All the women required medical therapy, 11 (55%) in an emergency room. It was concluded that individuals sensitised by occupational exposure to psyllium dust are at high risk for allergic reactions to ingested psyllium-containing products.

Another study reports the case of a 38-year-old female nurse who ingested a bowl of Heartwise, and 25 minutes later developed severe systemic anaphylaxis manifested by hypotension, a feeling of constriction in the throat, hoarseness, dyspnoea, wheezing, generalised pruritus, urticaria, and vomiting.

In general, allergic reactions to psyllium have been described as an occupational hazard among nurses and pharmaceutical workers who handle psyllium-containing laxatives. A 39-year-old female dialysis nurse had a 3-year history of nasal and eye symptoms from exposure to psyllium. She took a psyllium bulk laxative for constipation and developed flushing, tachycardia, urticaria, angioedema, laryngeal edema, and lightheadedness. An epicutaneous skin test and radioallergosorbent test for psyllium were both strongly positive. A 42-year-old female nurse with a history of asthma had allergic nasal and eye symptoms while dispensing psyllium. She received a prescription for crystallised psyllium, took it by mouth, and developed immediate flushing, tachycardia, urticaria, and angioedema. With subsequent ingestion of psyllium she also had severe wheezing, lightheadedness, and loss of consciousness. A psyllium epicutaneous skin test was strongly positive. It has been widely shown that occupational exposure to a psyllium-based powdered laxative in nurses may result in asthma and or rhinitis.

The personnel of 4 chronic care hospitals were evaluated by means of a questionnaire, and skin-prick tests with psyllium and various inhalants administered to 193 of 248 (78%) of the workers who agreed to participate. Seventy-five subjects (39%) had a history of respiratory symptoms in regular life and/or respiratory symptoms and/or rhinoconjunctivitis after handling psyllium. Six (3%) showed skin reactivity to psyllium. Increased specific IgE antibodies were found in 20 of 162 of the sera that were tested (12%). In the second part of the study, a histamine inhalation challenge was performed on 70 of 75 (93%) of the subjects with a history suggestive of asthma and/or occupational asthma and/or skin reactivity to psyllium. Twenty (29%) had significant bronchial hyperresponsiveness. The 6 subjects with a history suggestive of occupational asthma (n=3) and/or asthma (n=6) and/or positive skin test results to psyllium (n=6) had significant bronchial hyperresponsiveness and increased specific IgE levels. They all underwent specific inhalation challenges with psyllium in the laboratory. Four developed bronchospastic reactions (2 immediate and 2 dual reactions). It was concluded, with the inclusion of 4 cases initially reported in the year preceding the trial, that the prevalence of IgE sensitisation to psyllium was between 5 (skin testing) and 12% (increased specific IgE levels).

Of 743 surveyed health care workers who prepared psyllium laxatives for patients, 136 (18%) reported allergic events. Thirty-four of these employees (5%) reported shortness of breath, wheezing, or hives within 30 minutes after preparing psyllium laxatives.

A recent evaluation of the prevalence of psyllium-seed allergy among health care workers in geriatric care homes found the prevalence of sensitisation and clinical allergy to psyllium seed in the exposed group to be 13.8% and 8.6%, respectively. All the sensitised subjects had a positive prick test (8 of 58;13.8%) but only 4 (6.9%) of them were positive for specific IgE (> 0.35 kU/l). Five out of the 8 sensitized health care workers reported allergic symptoms on or after handling laxatives containing psyllium seed. All had rhinoconjunctivitis, and asthma was suspected in in 2 individuals. Asymptomatic sensitisation had occurred in 3 subjects. One subject with respiratory symptoms from psyllium had also experienced 2 anaphylactic reactions after ingestion of laxatives containing psyllium seed.

Occupational asthma has been described in pharmaceutical workers and nurses. Differing degrees of psyllium allergy were reported in 3 nurses. The reactions ranged from sneezing to chest congestion and wheezing. Allergy to psyllium may be brand-related: 2 did not report further symptoms when the brand was changed, suggesting that the granular form is less likely to result in allergy than the powdered form.

There is a report of 5 nurses aged 31-55 years having a history of asthmatic symptoms after exposure to psyllium that they prepared and distributed to patients. One subject – exposed for only 1 minute to the psyllium powder – experienced a severe immediate bronchospastic reaction, which required intubation for 3 hours; but she had complete functional recovery thereafter. Four of the 5 tested subjects had an immediate skin reaction to a commercial psyllium extract. All had IgE antibodies to psyllium. Inhalation challenges with psyllium caused isolated immediate (1 subject) and dual (3 subjects) reactions.

With the recognition of the importance of psyllium as an occupational allergen, precautionary steps have been instituted; this may have contributed to a reduction in the reports of adverse reactions to this allergen.

Anaphylaxis was reported in a 69-year-old nurse after psyllium ingestion; she presented with generalised body swelling, flushing and urticaria. She had experienced recurrent rhinitis and asthma related to psyllium exposure for the past 15 years while dispensing laxatives to patients. The diagnosis of psyllium hypersensitivity was established by a positive psyllium puncture-skin test, an elevated psyllium-specific IgE level in serum, and a confirmatory soluble-antigen competitive inhibition test.

Occupational allergy to psyllium, however, extends far beyond the immediate clinical setting and includes not only pharmaceutical manufacturing but cosmetics, fireworks, food, carpet and other textile manufacturing, hairdressing, printing, mining, and pharmaceutical research. Psyllium is a broadly important occupational allergen giving rise to asthma and rhinitis. The risk of sensitization to psyllium appears to be higher with laxatives in powder form than with granulated forms or with laxatives that produce fewer airborne particles. In general, psyllium seed sensitisation occurs after inhalation of psyllium seed powder, the particles of which can be as small as 2µm.

Exposure to psyllium dust in a pharmaceutical factory resulted in chest tightness/wheeze, nasal, ocular or skin symptoms in 48 of 92 exposed workers. While symptoms were not incapacitating in the majority (n=44) of these, 1 worker required antihistamines and 3 others experienced severe respiratory symptoms when exposed to the dust. It was concluded that handling psyllium produces a moderate irritant effect in most exposed people, but that sensitisation to the dust can provoke severe respiratory symptoms.

Of 140 employees of a psyllium-producing company, 39 had a history suggestive of occupational asthma; 23 of 120 (19%) showed a positive skin prick test to psyllium, and 31 of 118 (26%) had increased specific IgE antibodies; 39 (32%) workers had at least 1 of these 2 features.

In a cross-sectional study of 125 workers engaged in the manufacture of bulk laxatives based on psyllium husks and senna pods, skin-prick tests with extracts revealed that 7.6% were allergic to psyllium and 15.3% to senna. Four (3.2%) cases of occupational asthma were identified.

Occupational asthma occurred in a 19-year old male involved in the processing of psyllium, who reported an irritating cough on getting up in the morning.

Sixteen workers with normal nonspecific bronchial reactivity (NSBR) had been previously diagnosed with occupational asthma caused by high-molecular-weight agents: flour in 7 workers, psyllium in 5, and guar gum in 4. They were re-challenged after they had been removed from exposure to these agents for a mean of 5.7 years, no longer showed evidence of persisting asthma, and had a normal lung function. The authors concluded that specific bronchial reactivity to high-molecular-weight agents persists in most cases despite a normalisation of NSBR, and that this persistence is associated with a persistence of specific immunisation to the agents in question.

However, psyllium is not exclusively an occupational allergen. Two years after initiating regular psyllium-containing laxative use, a 40-year-old woman presented with a pruritic macular, papular, and urticarial rash involving the entire body, including the palms, soles and oropharynx, and sparing only the face. There was an associated sensation of chest and throat tightness and lip swelling. The signs and symptoms resolved upon discontinuance of the psyllium and recurred immediately after the patient initiated a challenge test. RAST for psyllium-specific IgE was positive. Anaphylaxis following ingestion of a laxative containing psyllium has been described in two studies. Skin test for psyllium was positive, and specific IgE elevated for psyllium seed.

A 31-year-old atopic woman, who handled a laxative containing P. ovata seeds at home, is reported to have developed asthma as a result. Psyllium may act as a potent inhalant allergen capable of eliciting asthma symptoms not only in an occupational context but also in a domestic environment, affecting consumers of this laxative or others who handle it.

Cross-Reactivity

A close phylogenetic relationship exists between P. ovata (psyllium) and P. lanceolata (English plantain); both are members of the same genus in this family. While most cross-reactivity studies between P. ovata seed and P. lanceolata pollen allergens suggest a lack of cross-reactivity, at least one showed the existence of immunologic cross-reactivity between P. ovata seed and P. lanceolata pollen. A recent study reported that “mild” cross-reactivity existed between P. ovata seed and P. lanceolata pollen was observed.

The major allergen of English plantain, Pla l 1, displays significant sequence homology with the major olive pollen allergen Ole e 1. But Pla l 1 was not detected in psyllium or melon extracts.