A lack of vitamin A can lead to rough and dry skin, respiratory infections, and dry eyes. A lack of vitamin B1 can cause indigestion, a poor complexion, numbness in the hands and feet, and may lead to beriberi and foot diseases. A lack of vitamin B2 can result in bad breath, insomnia, headaches, and mental fatigue. A lack of vitamin B12 can cause pale skin, thinning and yellowing hair, lethargy, poor appetite, and vomiting and diarrhea. A lack of vitamin C can lead to swollen and purple gums, easy bleeding in the gums, eye membranes, and skin, and poor wound healing. A lack of vitamin D can cause excessive sweating on the head, rickets in children, and osteomalacia in adults.