Dust balls are skittering across the floors, something dark green seems to be growing where the bathtub meets the tiled walls and your toddler is burying her face in the cat's soft fur. Is it time to freak out?
No; it's time to relax, said Eric Gershwin, chief of the Division of Rheumatology, Allergy and Clinical Immunology at the UC Davis School of Medicine.
"The hygiene hypothesis strongly suggests that, as a general rule, being compulsively clean isn't necessarily good," he said. Gershwin said that it's good for the immune systems of humans – particularly young children – to be exposed to a variety of materials in the air and elsewhere. Young immune systems need to be "educated," he said.
One important example of this, he said, is the immunity that comes with breast milk. Substances in breast milk have been proven to boost the immunities of breast-fed infants so that they typically have fewer problems with allergies as they grow older.
"That's one of the strongest arguments for breastfeeding," he said. "And that's why we recommend breastfeeding every chance we get."
In the end, common sense is the best guide when applying the hygiene hypothesis to everyday life.
"It's good to educate the immune system to a variety
of materials, but, if you have a family history of allergies and eczema, don't go out and buy
10 cats," Gershwin said.
"Everything in moderation.".