In 1925, Van Leeuwen and colleagues described a remarkable frequency (50%) of mould skin sensitivity in Dutch asthmatics principally to Mucor, Penicillium and Aspergillus spp[i]. In 1928 both Hansen[ii] in Germany and Jimenez-Diaz[iii] with colleagues reported positive skin tests to crude extracts of fungi.
The European Community Respiratory Health Survey showed 36% of with asthma had one or more positive skin prick tests, defining that person as atopic. Of these, 4.4% were sensitized to Alternaria and 2.3% were sensitised to Cladosporium compared with 21% sensitized to house dust mite, 17% sensitized to grass pollen and 10% sensitized to cat. Fungal sensitisation is much less common than other sensitisations in the general population in Europe, but more common in those with severe asthma.
Link with severe asthma
Fungal sensitisation is more prevalent in people with severe asthma. Approximately 25% of adult asthma patients referred to specialists and up to 75% of patients with severe asthma requiring multiple hospital admissions are sensitized to one or more fungi[iv]. Patients with severe asthma and fungal sensitization have SAFS
Issues with skin tests
Unfortunately reagents from different manufacturers differ and give slightly different skin prick test results in different people. Skin test responses may vary over time in the same individual even if performed in an identical manner with the same reagent. Asthma may also ‘go through good and bad periods’, possibly consistent with this. While the correlation between positive skin tests and IgE RAST test on blood is reasonable, there is enough discordance to require both to be done to identify all patients who are sensitized to fungi. Skin tests tend to be more sensitive. Some clinics test for a wide range of fungal sensitivity, others test for a limited number or only for Aspergillus fumigatus sensitivity. A reasonable minimum testing set is A. fumigatus, Candida albicans, Cladosporium herbarum, Alternaria alternata, Penicillium chrysogenum (notatum) and Trichophyton mentagrophytes.
An example of skin prick testing on the arm showing positive reactions to the positive control (histamine), and negative reaction to the negative control. Positive reactions to house dust mite (D pteronysinus), cat, grass and Cladosporium. A positive reaction is a raised area at least 3mm in diameter.
Another example of skin allergy testing showing a reaction to the positive control (+, histamine) and to grasses. The 'cat' reaction was less than <33mm, the criteria for a positive result.
The following video demonstrates the technique of skin testing for all types of allergen including fungal.
[i]Van Leeuwen WS, Nien Z, Kremer, W, Varenkamp H. Ztschr Immunitatsforsch 1925;44:1.
[ii] Hansen K. Uber schimmelpilz-asthma. Verhandl Deutsch Gesellsch Inn Med1928;40:204.
[iii] Jimenez-Diaz C, Sanchez Cuenca B, Puig J. Climatic asthmas. J Allergy 1932;3:396-403.
[iv] O'Driscoll BR, Hopkinson LC, Denning DW. Mold sensitization is common amongst patients with severe asthma requiring multiple hospital admissions. BMC Pulm Med. 2005;5:4.