What could be causing head and lip paresthesia that started during salmonella gastroenteritis?

Possible side effect: Although parasthesias don't commonly occur with Salmonella gastroenteritis

Gastroenteritis: It is tough to say but vomiting or diarrhea can lead to electrolyte imbalances such as hypokalemia which can in turn lead to muscle cramping. Oral parasthesias classically are associated with low calcium levels. Regardless, be sure to adequately hydrate yourself if unable to eat.