That's what I used to get but if you put a lot of shaving cream or soap on (like so much that it's hard to see your skin) then shave but don't press too hard of your legs, you shouldn't see any redness. But sometimes it's just how people's skin is. Hope I helped! ;))
Shave while taking a bath, not in the shower, so the hair becomes softened before shaving. Make sure you have a good lather of soap, or use one of the shaving gels available. Use a sharp razor and don't press down hard. Towel off gently when you get out of the bath and apply moisturizing lotion.
Scrub your legs lightly after sitting in the tub for 10-15 min's then apply antibacterial to clean them off good (may sting). apply a generous layer of soap (preferably one that's used for babies), shave carefully and rinse your shaver - after each stroke - in clean water. pad your legs gently with a towel when drying them and apply aloe vera moisturizing cream. try avoid drinking any caffeine eg. coffee or energy drinks at least 12 hrs before shaving - they tend to dry out your skin - . if it's really bad then apply deodorant - alcohol free - on the legs roughly 15min's before starting the scrub and antibacterial treatment. this has worked for me and my case is bad and I also used to get ingrown hairs, so my dermatologist gave me these tips and it worked really well on my legs as well as the bikini area. good luck! =)