Ow. Ow. Ow.

I was with some friends the other day and we started talking about sunscreen. One of them told us about some sunscreen she'd found that blocked both UVA and UVB. We talked about the relative effectiveness of various sunscreens we had tried.

I told them that I always use the sunscreen I get in New Zealand, put out by the Cancer Society. I was pretty sure it blocked UVA and UVB, and I thought that the Cancer Society would know what they were doing. One of my friends asked when I bought it.

"Oh, a couple of years ago," I said. I thought for a moment. "Maybe three or four years, actually. Or ... five?"

"It might not work anymore," she said. "What's the expiry date?"

Expiry date? I hadn't even thought about that.

When I got home I couldn't find an expiry date on the sunscreen. But was it not working? I'd been thinking I was getting a bit more colour than I usually do, but had attributed that to spending more time down by the river than I usually do in summer. What if the sunscreen wasn't working? My father got skin cancer. It was found quickly, and easily removed, but still, I know I should be careful.

Today I went down to the river again. Usually I wear sunscreen on my face, arms, hands, neck and shoulders. And usually I wear cotton trousers, and sneakers, so I don't worry about my legs and feet.

Today I wore a skirt and sandals. It was hot, and I thought it would be nice to get some sunshine and air on my legs and feet. I applied sunscreen in all the usual places, but I did not put sunscreen on my legs or feet. This is because, er, because, er ... um ... because ... I had a moment of spectacular idiocy? No, wait! It was a scientific experiment! To find out whether my sunscreen was still working! Yes, that's it! My legs and feet were the controls.

I went to the river, took some pictures, and came home after about an hour and a half.

My scientific experiment was extremely successful. I can now tell you, from experimental evidence, that my sunscreen is working very well indeed. My arms, hands, shoulders, neck and face are not bright red and radiating heat and making me walk funny.