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

Allergen Exposure

Geographical distribution
Guavas are native to Central or South America but now grow in many countries. Guava was said to be a favourite food of the Incas and Aztecs. The trees are among the most gregarious of fruit trees.

 

A small tree with spreading branches, the Guava is easy to recognise because of its smooth, thin, copper-colored bark that flakes off, showing the greenish layer beneath. The fruit, exuding a strong, sweet, musky odour (attributed to carbonyl compounds), may when ripe be round, ovoid, or pear-shaped. It has a thin, light-yellow skin, frequently blushed with pink. Next to the skin is a layer of somewhat granular flesh of varying colour and flavour. The central pulp is juicy and normally filled with very hard, yellowish seeds.

 

Environment
It can be a home fruit tree or planted in small groves. In many parts of the world, the Guava runs wild and forms extensive thickets, overrunning pastures, fields and roadsides so vigorously that it can be classed as a noxious weed subject to eradication. Nevertheless, wild Guavas in some countries (though underutilised) constitute the bulk of supply for major industries.

 

Raw Guavas can be eaten out of hand but are preferred seeded and served sliced as dessert or in salads. The sweet yellow fruit is eaten fresh; the pulp of the red, sour varieties is used for jelly, juices, etc. More commonly, the fruit is cooked, as cooking eliminates the strong odour. There are innumerable recipes for utilising Guavas in pies, cakes, puddings, sauces, ice cream, tapioca, juice, syrup, jam, butter, marmalade, chutney, relish, catsup, breakfast cereal, baby food and other products. Guavas may be canned or frozen, and extracts provide flavourants, pectin for food processing, and vitamin C for enrichment. Besides vitamin C, Guavas are a good source of potassium and fibre.

 

The roots, bark, leaves, shoots, and immature fruits are astringent. They are also thought to be analgesic, emmenagogue, febrifuge, and vermifuge, and are used for a variety of ailments both internal and external.

 

Unexpected exposure
The wood is used in carpentry, turnery, engravings and other ornaments, etc., but is not durable when wet. It is good firewood and also a source of charcoal.

 

The leaves, bark and young fruit are rich in tannins and other volatile compounds. The bark is used in Central America for tanning hides. The leaves with other plant materials make a black dye for silk, cotton, and matting.

 

Allergens
No allergens from this plant have yet been characterised.

Potential Cross-Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected; also often to the different species of the genus Melaleuca, and occasionally to Eucalyptus and other genera of the family Myrtaceae (1). Rose-apple and Clove are the closest related members of this family, which includes the Bottlebrush tree (Callistemon citrinis), Feijoas (Feijoas sellowiana), the Eucalyptus tree (Eucalyptus species), the Melaleuca tree (Melaleuca leucadendron), and the Melaleuca tea tree (Melaleuca alternifolia).

 

IgE antibodies were found to Peach, Guava, Banana, Mandarin and Strawberry in a patient experiencing anaphylaxis after eating Peach. The cross-reactive protein was identified as a 30 kDa protein occurring in all the fruits (2).

Clinical Experience

IgE-mediated reactions
Guava may uncommonly sensitise or induce symptoms of food allergy in sensitised individuals (2).

 

Allergic contact dermatitis due to Guava tea has been reported (3).

 

Other reactions
In Chinese medicinal folklore, Guava was useful in the treatment of diabetes mellitus. A study shows that Guava produced a marked hypoglycemic action in mice (4).

Compiled by Dr Harris Steinman, harris@zingsolutions.com