You have mentioned a history of ear infections, yet the title of the post mentions enlarged glands under the jaw area, which I presume are enlarged lymph nodes.
Ear infections, or more commonly ear inflammation, may be caused by numerous underlying reasons. While water is commonly mentioned by worried owners as a reason, in my opinion it is much less likely and common than one hears (no pun) about. After all, we swim, get water in our ears and dont necessarily suffer from outer ear disease because of it. Many bird dogs (Labs) are intended to swim and love to do so. There usually is another reason for repeated ear problems other than just water.
Sometimes its anatomical with narrow or flattened ear cartilages not allowing good drainage or air circulation. Most often allergies are involved.
Very commonly, allergies may lead to inflammation of the skin that lines the ear canals and ear flap ("pinna"). Inflammation makes that skin more porous allowing bacteria already there to penetrate more deeply into the skin than is normal and infection may ensue. The infection may include bacteria, yeast or both. A MAJOR contributing factor to the severity of the "ear infection" signs an owner may see is the degree of self-trauma caused by the dog itself. Head shaking (ear slamming on head), head rubbing (on ground) and scratching with paws all play a role in this, to varying degrees in any individual dog. That is why the "Elizabethan" (cone-like) collars and similar products are so effective in helping to resolve ear problems, by sharply limiting the self trauma that dogs are so good at creating.
By the way, allergies in dogs are most commonly due to environmental substances like pollen, mold spores or other environmental protein materials like dander, including human dander, and various insects or dusts from the insects decomposition in the environment. Perhaps 95% of dog allergies are related to such substances with another 5% due to protein materials ingested in food. With such a wide difference in the odds, its no wonder that true food allergy is so much less commonly diagnosed than environmentally caused allergies. Of course many people pursue this diagnosis with food changes, but in such cases food changes alone will not manage the problem. Sometimes dogs may have both allergies and specific diet changes help a little. It is truly a complex area and that is why your doctor is best situated to help you navigate the nuances of skin and ear disease related to allergy, if that is what is going on.
Most significantly, and unlike in people, symptoms of allergy in dogs are expressed not primarily through upper respiratory signs like coughing or sneezing but as skin disease and ear disease that often has a seasonal course.
In the case of a single sided ear infection or inflammation one worries about a deeper problem, perhaps a middle ear inflammation or infection which may or may not include a perforated ear drum.
The swelling of lymph glands in a region of the body implies that an inflammatory or infectious process exists in the region drained by those glands and should be evaluated. Swollen lymph nodes may be aspirated (punctured with a needle and fluid drawn out to test). A significant middle ear infection could cause swollen glands in that area. Of course another process (dental, other infection, tumor, etc) may also exist.
Lethargy is nonspecific and may accompany any condition being discussed and others. The response to antibiotics may indicate an infection existed. But why and where? Those are the questions needing answers to determine the problem is truly resolved.
In a three year old I'd be thinking infection or inflammation first. In any case, such a complicating factor as a lymph node enlargement means you need your veterinarian to pursue this thoroughly. Level with him or her about your concerns and allow him or her to work up the problem thoroughly.
Good luck and let us know how it turns out!
Arnie Goldman DVM
I completely agree with Dr. Goldman, this sounds like a very serious infection and aggressive workup and treatment are indicated. With the history of ear infections and itchy skin, an underlying allergic cause such as food allergy or pollen/dust allergies are suspected, and when an ear infection becomes chronic it can descend into the middle and inner ears, causing pain, lethargy, and balance problems. Due to the severity of the problem, I suggest talking to your veterinarian about referral to a veterinary dermatologist for more thourough evaluation of the ears, which may include video-otoscopy and deep ear flush, CT scan, ear cultures/2-3 month course of antibiotics based on culture results, and workup of the underlying allergic disease.
Kimberly Coyner DVM DACVD