What did the researchers want to find out?

Do children have higher odds of developing respiratory problems in homes with a higher frequency of cleaning product use? Jaclyn Parks from the Simon Fraser University in Vancouver, Canada, and her team investigated this hypothesis.

How did they proceed?

The research team regularly collected data from a total of 2,022 infants from birth until three years of age. For example, they asked the parents which cleaning products they used and how often they used them, what their children ate and what they were exposed to in the environment.

The children underwent physical examinations and gave urine samples. Skin prick tests were conducted at one, two and three years of age.

Based on a point system (Frequency of Use Score – FUS), the researchers assessed the usage frequency of cleaning products from 26 categories. The FUS score ranged from zero points for ‘never’ to four points for daily use. Three groups emerged out of the total point score:

• Group 1: less than 27 points
• Group 2: 27 to 35 points
• Group 3: over 35 points.

What were the results?

At the age of three, nearly 14 per cent of the children had developed allergic reactions. Nearly 9 per cent suffered from recurrent respiratory symptoms, and 6.4 per cent had asthma.

An average of 31 different cleaning products were used, most frequently:

• Washing up liquid and dishwashing detergent
• All-purpose cleaner
• Scented detergent
• Toilet cleaner

The more frequently the children were exposed to the cleaning products, the more likely they were to develop respiratory problems and asthma. This was especially the case for cleaning products containing perfumes.

Starting with the lowest FUS score in Group 1, the odds of developing recurrent respiratory symptoms rose by 49 per cent and asthma by 37 per cent in Group 2. An increase was also seen between Group 2 and Group 3.

Why is this study important?

Excessive cleanliness can have exactly the opposite effect from the one intended.

• First of all, cleaning products kill the germs that challenge infants’ immune systems and normally strengthen them against later infections and allergies.
• Second, the products contain more than 100 different chemicals, many of which directly irritate the airways.

Original study

Parks J et al. Association of use of cleaning products with respiratory health in a Canadian birth cohort. CMAJ. 2020;1925(7):E154-E161.