Maize, Corn

Further Reading

 Maize/Corn f8

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Code: g202
Latin name: Zea mays
Source material: Pollen
Family: Poaceae (Gramineae)
Sub family: Panicoideae
Tribe: Andropogoneae
Common names: Maize, Corn
Maize/Corn pollen (Zea mays) g202 must be differentiated from Maize/Corn (Zea mays) f8, the food.
A grass species producing pollen, which may induce hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution
The original habitat is obscure; it was probably South America or Mexico. The plant is now grown anywhere in the world where summers are reasonably warm. Corn is one of the most commonly grown foods. It is the staple cereal of the human diet in Central and tropical South America and in many parts of Africa. It is extremely important in livestock rearing, food processing and other commercial activities in developed countries.
The plant is a single-stemmed annual, grown from one seed, though sucker shoots (which may produce seed) rise from the base. The single stalk, terminating in the tassel or staminate flowers, can grow to over 3 m at a fast rate. The smooth leaves, usually drooping, usually green, can be over half a metre long.
The flowers are monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and are pollinated by wind. The female flowers are borne on a receptacle, termed "ear," which arises at a leaf axil near the mid-point along the stem. Normally 1 to 3 or more such ears develop. The flower organs, and later the grain kernels, in more or less longitudinal rows, are enclosed in several layers of papery tissue, termed husks. Strands of "silk", actually the stigmas from the flowers, emerge from the terminals of the ears and husks at the same time the pollen from the terminal tassels is shed. In the Northern Hemisphere it is in flower between July and October, and the seeds ripen between September and October. The grains are variable as to size, shape, and colour.
Sweet corn is distinguished from field corn by the high sugar content of the kernels at the early "dough" stage, and by wrinkled, translucent kernels when dry.
The plant is found in cultivated beds, and does not grow wild except when escaping cultivation in a very limited way.
Maize is eaten straight off the cob or processed in a variety of ways.
Unexpected exposure
Maize pollen may be used in herbal therapies. The stalks, cobs, grains and oil have many agricultural and industrial uses.
  • Zea m13, an allergen having significant sequence homology with a number of pollen- or anther-specific proteins from monocot and dicot plants as well as with recently described allergens from Olive and Rye grass, has been isolated. The recombinant Zea m13 fusion protein reacted with serum IgE from grass pollen-allergic patients, indicating that Zea m13 and homologous proteins represent a family of conserved plant allergens (1).

Potential Cross-Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected, as well as to a certain degree among members of the family Poaceae, and is especially likely among Bahia grass (g17), Johnson grass (g10) and Maize pollen (g202), related through the sub-family Panicoideae (2-3).

However Maize pollen in several studies has shown lower degree of cross reactions than other grasses, see below.

This grass contains one of the Group 1 allergens, which are glycoprotein isoallergens shared by many species of grass (4). Group 1 allergens are highly homologous, but not all of the antigenic epitopes are crossreactive (5). For example, Group 1 allergens from eight different clinically important grass pollens of the Pooideae (Rye grass, Canary grass, Meadow grass, Cocksfoot and Timothy), Chloridoideae (Bermuda grass) and Panicoideae (Johnson grass, Maize) were isolated, and IgE binding to an allergic human serum pool was conducted to determine the degree of antigenic and IgE-binding similarities. The highest IgE-binding similarity was observed between Cocksfoot and Rye grass (53%) and between Rye grass and Canary grass (43%). No IgE-binding similarity was observed between Maize and other grasses. The highest antigenic similarity was also observed between Rye grass and Cocksfoot grass (76%), and the lowest similarity between Maize (23%) and Bermuda (10%) (6). 

Maize pollen appears to also contain a Group 5 allergen. Almost 90% of grass pollen-allergic patients are sensitised against Group 5 grass pollen allergens. A monoclonal human IgE antibody has been shown to cross-react with Group 5A isoallergens from several grass and Corn species however no reactivity was observed with maize (7). 

The cross-reactivity of IgE antibodies to Group 1 and Group 5 allergens has been shown to be highly variable in 8 grass pollen species. Cross-reactivity of IgE antibodies against Lol p I or Lol p V (both from Rye grass pollen) to Dactylis glomerata (Cocksfoot), Festuca rubra (Red Fescue), Phleum pratense (Timothy), Anthoxanthum odoratum (Sweet Vernal grass), Secale cereale (Cultivated Rye), Zea mays (Maize/Corn), and Phragmites communis (Common Reed) was investigated by means of RAST-inhibition. Within a group of sera the degree of cross-reactivity was demonstrated to be highly variable. Individual sera were not always equally cross-reactive to all pollen species. A high degree of cross-reactivity for Group 1 allergens did not necessarily imply the same for Group 5. Group 1 and Group 5 representatives were found to be present in all 8 species (8).
Later studies have shown contradictory results and Zea mays may in fact not contain a Group 5 allergen (nor a Group 2 allergen) (9).

Clinical Experience

IgE mediated reactions
Z. mays pollen is found in lower concentrations in aerobiological studies because of its density. Nevertheless, individuals exposed to this pollen may have asthma, allergic rhinitis and allergic conjunctivitis induced (10-12).  
In a study of 101 patients with asthma living in Comarca Lagunera, Spain, specific IgE determination tests demonstrated that 57% of the group were sensitised to Maize pollen (10). Z. mays pollen was also shown by specific IgE tests to be an important pollen among 614 respiratory-allergic patients in Turkey (13).
In 468 asthmatic children in Johannesburg, South Africa, the commonest allergens on specific IgE testing included Maize/Corn pollen (14).
Other reactions
Thirty-three Navajo patients were seen in a private allergy consultation practice in Flagstaff, Arizona. Skin test and historical data were available from 9 atopic patients to evaluate hypersensitivity reactions to oral corn pollen used in the Navajo ceremonials. Six of the nine patients had positive skin test reactions to Corn pollen and four of these six reported symptoms from oral Corn pollen. The symptoms included various combinations of oral and ear itching, sneezing, cough, and wheezing (15).

Compiled by Dr Harris Steinman,


  1. Heiss S, Flicker S, Hamilton DA, Kraft D, Mascarenhas JP, Valenta R. Expression of Zm13, a pollen specific maize protein, in Escherichia coli reveals IgE-binding capacity and allergenic potential. FEBS Lett 1996;381(3):217-21 
  2. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09 
  3. Yman L. Pharmacia: Allergenic Plants. Systematics of common and rare allergens. Version 1.0. CD-ROM. Uppsala, Sweden: Pharmacia Diagnostics, 2000. 
  4. Hiller KM, Esch RE, Klapper DG. Mapping of an allergenically important determinant of grass group I allergens. J Allergy Clin Immunol 1997;100(3):335-40 
  5. Esch RE, Klapper DG. Cross-reactive and unique Group I antigenic determinants defined by monoclonal antibodies. J Allergy Clin Immunol 1987;78:489-95 
  6. Suphioglu C, Singh MB, Knox RB. Peptide mapping analysis of group I allergens of grass pollens. Int Arch Allergy Immunol 1993;102(2):144-51 
  7. Flicker S, Vrtala S, Steinberger P, Vangelista L, Bufe A, Petersen A, Ghannadan M, Sperr WR, Valent P, Norderhaug L, Bohle B, Stockinger H, Suphioglu C, Ong EK, Kraft D, Valenta R. A human monoclonal IgE antibody defines a highly allergenic fragment of the major timothy grass pollen allergen, Phl p 5: molecular, immunological, and structural characterization of the epitope-containing domain. J Immunol  2000;165(7):3849-59 
  8. Van Ree R, Driessen MN, Van Leeuwen WA, Stapel SO, Aalberse RC. Variability of crossreactivity of IgE antibodies to group I and V allergens in eight grass pollen species. Clin Exp Allergy 1992;22(6):611-7 
  9. Niederberger V, Laffer S, Froschl R, Kraft D, Rumpold H, Kapiotis S, Valenta R, Spitzauer S. IgE antibodies to recombinant pollen allergens (Phl p 1, Phl p 2, Phl p 5, and Bet v 2) account for a high percentage of grass pollen-specific IgE. J Allergy Clin Immunol 1998;101(2 Pt 1):258-64 
  10. Martinez Ordaz VA, Rincon Castaneda CB, Lopez Campos C, et al. Cutaneous hypersensitivity in patients with bronchial asthma in La Comarca Lagunera. [Spanish] Rev Alerg Mex 1997;44(6):142-5 
  11. Riggioni O, Montiel M, Fonseca J, Jaramillo O, Carvajal E, Rosencwaig P, Colmenares A. Type I hypersensitivity to gramineae pollen (by species) in allergic rhinitis patients. [Spanish] Rev Biol Trop 1994;42 Suppl 1:71-6, 20 
  12. Van Niekerk CH, De Wet JI. Efficacy of grass-maize pollen oral immunotherapy in patients with seasonal hay-fever: a double-blind study. Clin Allergy 1987;17(6):507-13 
  13. Guneser S, Atici A, Cengizler I, Alparslan N. Inhalant allergens: as a cause of respiratory allergy in east Mediterranean area, Turkey. Allergol Immunopathol (Madr) 1996;24(3):116-9 
  14. Green R, Luyt D. Clinical characteristics of childhood asthmatics in Johannesburg. S Afr Med J 1997;87(7):878-82 
  15. Freeman GL. Oral corn pollen hypersensitivity in Arizona Native Americans: some sociologic aspects of allergy practice. Ann Allergy 1994;72(5):415-7

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.