One of the first lessons veterinary students learn is a simple phrase that stays with them throughout their careers: common things are common.

It sounds almost too obvious but it is one of the most important principles in medicine.

Every day we are presented with pets showing symptoms that could have dozens of possible causes.

While it is tempting to jump straight to the rare diseases we have all read about, good veterinary medicine starts by ruling out the simple, common explanations first.

Take itchy skin, for example. We certainly see allergies, autoimmune diseases and hormonal disorders in Bermuda but by far the most common reason a dog or cat is scratching is fleas.

Bermuda’s warm, humid climate means fleas thrive all year round, not just during the summer. Even a single flea bite can make some pets intensely itchy, particularly those with flea allergy dermatitis.

Before we start investigating more unusual skin conditions, it makes sense to ensure flea prevention is up to date, it’s cheaper for you too.

The same logic applies to weight loss. Serious illnesses such as cancer, diabetes and kidney disease can certainly cause a pet to lose weight but intestinal worms remain one of the most common and easily treatable causes, especially in younger animals.

A simple faecal examination and appropriate worming may solve the problem before more extensive investigations are needed.

Diarrhoea is another classic example. There are countless diseases that affect the digestive system but one of the first questions we ask is: “Has your pet eaten anything different?”

In many cases, the answer is yes. Whether it is rich leftovers from a summer family barbecue, a new brand of treats, food stolen from the kitchen bin or simply eating something unpleasant while out on a walk, dietary indiscretion is one of the leading causes of stomach upsets we see.

Most cases settle quickly with appropriate treatment and a bland diet, avoiding the need for expensive tests.

Then there is obesity. Owners are often convinced there must be an underlying medical problem causing their pet to gain weight. Although hormonal conditions such as hypothyroidism or Cushing’s disease do occur, they are relatively uncommon. Far more often, the explanation is much simpler: too many calories.

Those calories rarely come from the main meal alone. They come from biscuits with morning coffee, treats after a walk, scraps while preparing dinner and rewards simply because those hopeful eyes are difficult to resist.

Individually they seem insignificant but together they can add hundreds of extra calories every day. We all like to show love through food and our pets are very good at convincing us they are hungry.

The challenge is remembering that they rely entirely on us to make healthy decisions on their behalf, which means sometimes limiting the treats.

Of course, common things are not the only things. Sometimes the flea treatment is current, the worming is up to date, the diet has not changed and the weight gain cannot be explained. That is when we dig deeper with blood tests, imaging and more specialised investigations.

Veterinary medicine is often compared to detective work and like any good detective, we start with the most likely suspects before chasing the unlikely ones.

It saves time, reduces unnecessary expense and, most importantly, gets pets feeling better sooner.

So, the next time your veterinarian asks what might seem like simple questions about flea prevention, worming, diet or treats, remember there is a reason. Before we look for zebras, we first need to rule out the horses.

Because in veterinary medicine, common things really are common.

• Lucy Richardson graduated from Edinburgh University in 2005. She started CedarTree Vets in August 2012 with her husband, Mark. They live at the practice with their two children, Ray and Stella, and their dog and two cats. She is also the FEI national head veterinarian for Bermuda