Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain it seems that along with Sinus infection there is also dry mouth also known a Xerostomia leading to cracks on tongue and roof of mouth.. Dry mouth can occur due to a number of causes like side effects of medicines, salivary gland disorders, dehydration, mouth breathing, oral yeast infection also known as Oral Thrush etc. It can be yeast infection if you have white coating over the tongue.. As dry mouth leads to inflammation of the mucosa of the tongue, it can lead to sensitivity and in the absence of sufficient saliva taste buds cannot function properly leading to diminished taste.. I would suggest you to consult an Oral Physician and get evaluated and a thorough clinical evaluation can help in diagnosis and treatment will depend upon the cause.. You can be advised to chew sugar free chewing gums as it help in stimulating saliva flow.. Gargle with specialized mouthwash formulated for dry mouth individuals like Biotene mouthwash.. Drink plenty of water.. Avoid spicy food and take a soft diet.. Maintain a good oral hygiene.. In case of thrush antifungal mouthwash like Nystatin, Clotrimazole lozenges and probiotics like Yoghurt can be advised.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.