Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain and presentation of symptoms swelling under the jaw during eating and that subsides once eating is stopped gives a clear cut diagnosis that there is swelling in the submandibular salivary gland which is a major salivary gland and it is due to clogging of the duct of the gland either with some foreign body or formation of crystalline stones [SIALOLITHS] from the minerals present in saliva.. Clogging of the duct obstructs the flow of saliva from the gland to mouth and when during eating the saliva flow increases, due to obstruction in the duct the saliva flows back into the gland causing swelling.. Nothing to worry, consult an Oral Physician and cross sectional x-rays or MRI SCAN can be advised for locating the stones and confirming the diagnosis.. At times stones located in ducts in the superficial location like floor of mouth can be located by palpation and the dentist can gradually push the stone towards the duct orifice and remove it manually.. Deeper stones are located by an endoscopic technique known as SIALOSCOPY and removed surgically.. As of now drink plenty of water and suck on sour candies as they will increase saliva flow and many a times stones gets flushed out with saliva and do not need treatment.. But in case if there is swelling and pain when doing the above remedy its better to consult an Oral Physician and get treated accordingly.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora..