And according to scientists, that parental instinct was right all along.
Children who come home splattered in mud after playing are less likely to develop allergies as they get older, the researchers found.
Up to no good! Playing in the mud could boost youngsters' immune systems
Their developing immune systems are exposed to a greater variety of bacteria than those of their cleaner counterparts, so they can cope better when germs are encountered later in life.
One in four of us now suffers from some kind of allergy, a figure that has risen in recent decades – as parents have become more worried about hygiene.
Professor Hans Bisgaard, who led the study, published in the Journal of Allergy and Clinical Immunology, said: ‘What matters is to encounter a large number of different bacteria early in life when the immune system is developing and 'learning'.
‘Our new findings match the discoveries we have made in the fields of asthma and hay fever.’