Casein, an important house dust allergen


  • House dust contains more milk casein than pet and mite allergens

The use of casein and gelatine (bone glue dust) in indoor plasters is not commonly known. In Finland, casein has been used since the 1960s to improve the handling properties of plaster. We measured casein in 91 house dust samples and compared the level to better known indoor allergens. Casein, cat (Fel d 1), dog (Can f 1) and mite (Der p 1, Der f 1) allergens were measured with the ELISA method (1).

Casein was detected in all but one dust sample. The median casein level was 30 µg/g (range 4–3300 µg/g), which was higher than those of pet animals and mites; cat 0.11 µg/g (range 0.01–1072 µg/g), dog 0.76 µg/g (range 0.01–2365 µg/g), Der p 1 < 0.01 µg/g (range < 0.01–366 µg/g) and Der f 1 < 0.01 µg/g (range < 0.01–15 µg/g). In 27 pure plasters the median casein content was 2.4 µg/g (range < 0.1–8300 µg/g). The highest level was in a floor plaster.

In this study, casein was measured in the settled dust. It is not know whether casein is airborne. Further, it is not known how commonly organic proteins are used in indoor construction materials. At least casein and egg proteins may be used in organic paints. Indoor casein may also be derived from food. However, high casein levels were detected in dusts from places where milk was not used (360 µg/g) or not allowed (laboratory office, 655 µg/g). In addition, casein was also high in dusts where no whey protein could be demonstrated.

Several manufacturers in Finland have changed from casein to synthetic materials in the 1990s. However, many houses still contain casein. Since 1982, casein has not been allowed in plasters in Sweden. It is difficult to estimate how much casein or gelatine-like compound containing surfaces still exist in housing stocks world-wide. One Dutch study exists in which a whey protein (β-lactoglobulin) was detected in house dust (2).

The added casein in a plaster is not easily recognized, because casein is not listed on the safety data sheet, since it is not considered harmful for health. However, death has been described after inhalation of milk proteins (3). Casein has also been used in latex gloves and allergic reactions have been described after skin contact to milk proteins (4).

In Nordic countries, pet dander is one of the most common indoor sensitizers, whereas mites are not considered important (5). In this study, casein was shown to be an abundant indoor allergen exceeding the more well-known animal and mite allergens. It should be considered whether airborne food allergens play a role in immediate skin allergy or in delayed-type food allergy and atopic eczema, especially in small children crawling in close contact to house dust potentially containing casein.

Accepted for publication 30 May 2002
Allergy 2002: 57:1084–1085
Copyright © Blackwell Munksgaard 2002
ISSN 0105-4538


This study has been supported by The Finnish Work Environment Fund.