To the Editor: The Hygiene hypothesis put forward to explain the increased incidence of autoimmune diseases over the past 50 years, including Type 1 diabetes, claims that the rising incidence could be due to reduced antigen stimulation or infection during infancy which could interfere with the development of the immune system [1]. In his For Debate article Dr. Gale [2] suggested that the missing link in the hygiene hypothesis could be related to Pinworm infections. In the 20th century 50% of European children were infested with Entrobius, but such an infestation nowadays has subsided dramatically, and infestation is now less frequent and intense than before [3]. In support of the Entrobius hypothesis, diseases such as Asthma and Type 1 diabetes have risen in Europe, possibly due to the loss of a protective influence of infestation.

To better clarify the role of hygiene in Type 1 diabetes, we decided to look at the personal care consumption expenditure in countries of the European Union for the same period where incidence data of Type 1 diabetes are available [4]. The personal care consumption was calculated by means of Purchasing Power Standards (PPS), which compare incomes (or other disposable amount of money) as well as expenditure in different countries. PPS indicates, for the various countries, the national currency units needed to purchase the same basket of goods and services (personal care including toiletries, hair and skin products). If currency values (e.g. an amount of received income) are converted into PPS, the resulting values are directly comparable in terms of the purchasing of households [5]. We have to take this data with caution since PPS reflect personal care for all the family and do not consider personal care consumption expenditure in childhood. Nevertheless, PPS represent the best available indicator of personal care in different EU countries.

We found a high statistically significant negative correlation between the incidence of Type 1 diabetes and personal care consumption, as reflected by PPS, in EU countries; that is, the higher the level of personal care, the lower the incidence of Type 1 diabetes (Fig. 1).

Fig. 1.
figure 1

The relation between incidence of Type 1 diabetes and Purchasing Power Standard (PPS) for Personal Care Use in Western European Countries (n=14). Correlation coefficient =−0.6855, two-tailed p=0.0068. List of countries for which PPS data and incidence figures for Type 1 diabetes are available include: Austria, Belgium, Denmark, Germany, Greece, Spain, France, Ireland, Italy, Netherlands, Portugal, Finland, Sweden, United Kingdom

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Our data are of particular interest because countries where PPS data were available were all members of European Union. In a recent paper [6] a series of indicators of national prosperity of countries with poor and high income across Europe were studied (not only EU countries) whereby the wide variation of Type 1 diabetes incidence rates could be partially explained by indicators of national prosperity. If by contrast we compare the incidence of Type 1 diabetes and Gross Domestic Product in only European Union countries selected for our analysis of PPS we did not observe any correlation (r=−0.05, p=NS), indicating that it is not the national prosperity which correlates with the different incidence of Type 1 diabetes within the EU. Therefore, our data do not support the hygiene hypothesis for Type 1 diabetes, on the contrary we think that high personal care may be protective from the development of Type 1 diabetes.

In conclusion, spending extra money on personal care may be a preventative measure for the development of Type 1 diabetes.