Do Allergies Protect Against Cancer?

One of the things I speculated about, with colleagues, back in the 1980s, was whether allergies may protect against cancer. These were the heady days when I was first declared the world’s “Number One Allergy Detective” (Sunday Mail, 1990).

We were dealing with a jumpy, overactive immune system, that’s for sure. Allergies are caused when the immune system attacks things that would be well left alone (like foods, danders, body tissues etc.).

But the big question was: would that over-activity of the immune system help by providing extra protection against cancer? Or would it work the other way and the jumpy, bit-crazy, immune system wasn’t really functioning well enough, as it should? That might give cancer an advantage over the body defences.

Well, I favored the protection view in these debates. But it was all opinion (mixed with a little experience and knowledge, of course).

Now we have a possible clue: a recent Danish study looked at almost 17,000 Danish adults who were tested for contact allergies between 1984 and 2008. About one-third (35%) tested positive for at least one contact allergy. Women were more likely than men to have a contact allergy — 41% versus 26%.

When the study authors examined cancer cases among the participants over the long term, they found that men and women with contact allergies had significantly lower rates of breast and non-melanoma skin cancer, and women with contact allergies also had lower rates of brain cancer compared to those without contact allergies.

Contact dermatitis is only one type of allergy, of course. But this result does suggest that an over-reactive immune system might give some protection against cancer.

But it wasn’t all positive. People with contact allergies had higher rates of bladder cancer. That’s the trouble with science; we don’t always get unequivocal answers.

Contact allergies occur due to direct contact with chemicals and common metals such as nickel.

[SOURCE: BMJ Open, news release, July 11, 2011]