Re: Does gluten cause acne? Shaving?
I personally do not subscribe to the dietary hypothesis: if you're between 16 and 20 and breaking out along your jawline, it is almost certainly hormonal. In-grown hairs are also quite easy to distinguish from standard acne lesions, because, on close inspection, you will typically see the hair growing back into the skin. I have also found that the number of blades one uses does not make a large difference, unless you happen to have extraordinarily sensitive skin. A good razor with a pivoting head, like the Mach3, should not contribute to the problem.
Openseason is right about shaving with the grain, but the hair often grows erratically on the neck and under the chin - try to get a good luck at the direction it's growing in and adjust your shaving stroke accordingly - it may be that you should be shaving up the neck, but down the cheeks and chin.