That's not how that works.

To blind a security camera, you need to exceed its static range in the area of the CCD that your face occupies.

If camera optics were perfect, you would have to lighten or darken your entire face to the extent that your face either maxed out or minned out the CCD at its current exposure setting. (So having a "too well" illuminated face would actually help hide from a camera that didn't adjust to the brightest object in the frame, which includes most security cameras.) This can take a fair amount of light. However, security camera optics usually suck, and due to low-res CCDs and low-quality and dirty lenses, even a few small light sources near your face can help over-expose and obscure your whole face. The light incident on the camera from a small IR LED is often more than sufficient to do this, especially if the camera has an exposure optimized for dark or indoor conditions. The extra light reflected from your skin due to wearing IR LEDs is unlikely to compare to the light emitted directly from the LEDs.

If you have any cheap cameras, you can text this yourself. A single small IR LED on a low quality IR-unfiltered camera looks like the lens flare from a JJ Abrams movie.

Maybe strap one of these [1] to your head, and make sure it's always pointed at the CCD.

Otherwise, not enough power. As @DanBC says, try it with LEDs. It doesn't work.

[1]: http://www.wickedlasers.com/torch

I have tried it; it doesn't work.

Can you point me to any video or picture of it working?

Are you trying it with an IR security camera? If not, it's probably IR filtered.

I think you shouldn't point the leds at your face, but away from it, so that the light has a chance to shine directly into the camera sensor.

LEDs just aren't very bright. This is an idea that people think works until they try it.

I agree with you that a typical 3mm/5mm LED will not be effective. There are some very high power LEDs nowadays, and I've just tried a 2003-vintage IR spotlight, made from four large LEDs, against the cheap cameras around the house. All of those are completely washed out by it. A nicer camera, which has an IR filter, is unfazed.