Question: how to know if you have zinc deficiency?
Answer: Skin, nails and hair. Zinc deficiency may manifest as acne, eczema, xerosis (dry, scaling skin), seborrheic dermatitis, or alopecia (thin and sparse hair). ... 
Mouth. ... 
Vision, smell and taste. ... 
Immune system. ... 
Diarrhea. ... 
Appetite. ... 
Cognitive function and hedonic tone. ... 
Psychological disorders.