Guajava - Guajava demonstrates antifungal, antibacterial, anti-inflammatory, laxative, and analgesic properties. It is used to treat herpes ulcers, ringworm, dermatitis, and urinary tract infections. Guajava is related to cassia and senna, and contains anthraquinones found in those other species as well.
Vitamins B, particularly biotin (vitamin B7) and B12 are important to keep healthy nails. If your nutrition lacks in vitamins B, nails will be dry and brittle. Vitamin C deficiency is associated to brittle nails and may cause infections of nail tissues.
Some infants with koilonychia do have iron deficiency, so see your baby's doctor if you notice this nail change. Vitamin B-12 deficiency can cause nail discoloration, including, brownish or blue nails or blue-black streaks not associated with ridges. Brown, black or white bands can also indicate malnutrition.