Hi Welcome to HealthcareMagic forum Weird smell of ammonia from the nose is due to drying up of the secretions in the nose. When the water content of the nose and the paranasal sinuses reduce in conditions such as inadequate water intake, nasal allergy, sinusitis, fungal infection of the nose, etc. there is foul smell emanated from the nose. In brief, the physiology of excretion of the waste (ammonia and uric acid) from the body involves skin and kidneys. To get rid of excess ammonia from the body it requires water as a transport medium. If there is no adequate intake of fluid, then the solution (ammonia and water) will not be diluted and ammonia is retained in the body. Hence, the foul smell from the nose is noticed only when you are dehydrated and not when adequately hydrated. Wish you good health Regards