Hello dear, The Clotrimazole present in the ear drop is of minimal concentration to be effective for topical application. Though one can feel some irritation when it comes in contact with the mucous membrane, the concentration is not sufficient enough to cause any systemic effect (like upset stomach) if absorbed through the mucous membrane. The stomach upset can be due to either any infection in the Gastrointestinal tract or Gastritis. So, if the symptoms still persist, kindly consult a Gastroenterologist & get a proper physical examination done. Investigations like complete blood count, stool examination, Ultrasound scan of abdomen will be helpful to rule out any pathology in the Gastrointestinal tract. You can ask me any further query using the below link: http://www.healthcaremagic.com/doctors/dr-polash-sannigrahi/64925 There is no need to worry, your husband will be fine. Wishing a good health. Take care.