The yellowish pigmentation visible in the photograph can sometimes be due to natural tooth colour or surface staining, but the fact that you develop significant pain on one side when eating raw onion or certain foods is more suggestive of tooth sensitivity, decay, gum recession or another local dental problem rather than pigmentation alone. Tooth decay can cause sharp pain with certain foods, and a cracked or damaged tooth can also produce similar symptoms.
Next Steps
Because the pain is localised to one side, I would recommend getting that particular area examined by a dentist, even if the pain comes and goes. An examination can determine whether there is a cavity, enamel wear, gum-related sensitivity or another dental cause. Do not try to whiten or aggressively scrub the yellow areas until the cause of the pain is clarified. For better treatment and personalised guidance, you may connect with us at 9 3 1 5 6 6 1 5 6 5 for proper treatment and guidance.
Health Tips
For now, avoid foods that trigger the pain, particularly very acidic, spicy or extremely hot/cold foods. Brush gently twice daily with fluoride toothpaste and clean between the teeth regularly. Avoid aggressive brushing, as enamel wear can contribute to sensitivity. If you develop facial/gum swelling, fever, severe persistent pain, pus or difficulty opening the mouth/swallowing, seek prompt dental care. Thank you