Your sideburns will grow back the same as they were. Shaving hair doesn't make it grow back thicker that is an age old myth. The hair as it begins to grow might appear thicker because the hair has been blunt cut straight across.

Best thing to do if you are self concious about that is to goto an esthecian and have them waxed. Gradually after you go back and back again....the hair will lessen in the amount of regrowth. You need to keep going back to get the waxed hairs all into the same growing cycle. Waxing will clean the hairs but after the first few times you could see hairs several days after waxing. But typically waxing lasts 2-4 weeks. And no it doesn't hurt as long as the person doing the waxing knows how to pull off the muslin strips away from your face. To give you a clue they should pull them off straight across your face.....not up and away from your face...because that is a poorly trained person and it will hurt because of the technique they are using. Also immediately upon removing the strip they should place their free hand over the waxed area to help sooth the area. If you have sensative skin ask for a wax for sensative skin.

Thats what I think is best for you.

G'luck