Dear Doctor: Neither of my sisters have pets, and all their kids have allergies. Could the fact that we have dogs, a horse and a barn cat be the reason that my kids aren't allergic to anything?

Dear Reader: How and why allergies develop are complex questions that have long been the subject of study. So many variables are at play, both genetic and environmental, that it's difficult to pinpoint why someone does develop an allergy and someone else does not.

That said, an emerging body of evidence suggests that early exposure to pets may indeed offer a measure of protection from developing an allergy. It's tied into what we're now learning about the importance of the gut microbiome, which is the array of microbes and microorganisms that coexist within our bodies. This insight offers new avenues of research and understanding that are both fascinating and intriguing.

Let's back up and talk about what, exactly, an allergy is.

An allergy develops when the immune system perceives a normally harmless substance as a threat and then mounts a vigorous defense against that substance. Dust mites, pollen, certain foods and pet dander are among the substances that the immune system may suddenly begin to target. The result of this hypersensitivity can manifest as itchiness, swelling, hives, wheezing, difficulty breathing, stomach upset and vomiting. Most allergies are manageable and are merely unpleasant or annoying. However, some allergic reactions can be so extreme that they are life-threatening.

The original idea behind the pets-are-good theory of allergy protection was that, through early exposure, individuals became desensitized to the presence of potential allergens. New research now suggests a connection between regular contact with animals and beneficial changes to the gut microbiome.

Some researchers believe that when a child is exposed to certain pet-associated microbes, the result is a beneficial effect on the development of his or her immune system. The theory is that the presence of animals adds a level of diversity to the microbes that the child encounters daily. The result is an immune system that's measurably less trigger-happy in the presence of potential allergens.

However, this exposure appears to be at its most effective before birth and during the first 12 or so months of life.

What's also interesting is that stool samples taken from children who grew up on a farm, and therefore came into regular contact with a variety of animals, had a broader diversity of microbiota than did samples from children living without pets. And it's not only contact with the animals themselves that scientists believe has benefits. The microscopic traces of soil that cling to the animals and get transferred to people, or that the animals bring into the home, contribute to an environment with a more robust and diverse array of useful microbes.

With research into the mysterious and fascinating microbiome still in its infancy, we can only imagine the revelations to come.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: We've lived in our house for years -- and raised three boys on well water. All have been reasonably healthy. But I recently learned that the well water's pH is 8.5-plus. Should we be concerned?

Dear Reader: The pH of water can range from acidic to basic on a scale of 1 to 14, with the pH of pure water at about 7. A pH less than 7 makes the water more acidic, while one greater than 7 makes water more alkaline (basic). The danger of more acidic water -- when the pH is less than 6.5 -- is that it can leach metals from the well and from the pipes that bring you water. These metals include lead, manganese, copper and iron, and they can be toxic in large amounts. So acidic water obviously poses a health risk. Fortunately, the same is not true of more alkaline water.

There has been no evidence of harm found in drinking water with a pH between 7 and 8.5. (Interesting to note: The pH of human blood is a little on the basic side, 7.365.) When the pH of water becomes greater than 8.5, it can taste more bitter. This elevated pH can also lead to calcium and magnesium carbonate building up in your pipes. While this higher pH doesn't pose any health risks, it can cause skin to become dry, itchy and irritated. So, if you or your children are having any skin issues, the pH of your well water could be a reason.

Many companies have advertised the benefits of alkaline water -- that is, waters with pH levels greater than 8.5. People who sell such products say that alkaline water has benefits in lowering blood sugar, improving gut health and improving the hydration of extreme athletes. None of this has been well-studied in humans. In addition, our kidneys are the best filtration system in maintaining the acid-base status within our bodies.

Because I can be somewhat obsessive about things, I support knowing the pH of one's well water, more to protect against excessive acidity than high alkalinity. For people with water pH less than 6.5, I would look at ways to make it more basic. Those with water pH between 6.5 and 8.5 can rest more easily. Even if it is greater than 8.5, the water is still probably safe, but you may want to acidify the water if you are noticing skin problems.

Lastly, whether bottled or from your own well, water is still the best drink choice. We live in a society where the consumption of water is intertwined with the use of sweeteners. This is seen not only in the plethora of sodas that we consume, but also in the number of juices, energy drinks, flavored waters and other drinks with chemical sweeteners.

Slightly high pH or not, plain water is the healthiest drink you can choose.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Can the food we eat affect chronic inflammation in the body?

Dear Reader: In our previous column, we addressed the first half of a two-part question about inflammation -- what it is, and how it can be affected by diet. In answering the first half of the question, we discussed the two main types of inflammation and how they take place.

To (briefly) recap: Inflammation is the body's immune response to a perceived threat. Acute inflammation, a short-lived reaction to injury, trauma or infection, causes swelling, redness, and a sensation of heat and pain. Chronic inflammation, a low-level reaction, takes place below the threshold of pain. As a result, it tends to fly under the radar. But unlike acute inflammation, which abates when the threat has been neutralized, chronic inflammation continues. It has been linked to heart disease, cancer, arthritis, diabetes, obesity and Alzheimer's disease.

Does what we eat have an effect on chronic inflammation? Research shows that yes, components of certain foods can activate the inflammatory response, and others inhibit it.

Unfortunately, many staples of the modern diet encourage inflammation. Refined carbohydrates and processed foods such as chips, sodas, sugary breakfast cereals, luncheon meats, fried foods, red meat, candy bars, breakfast pastries, and that addictive blended mocha with a swirl of whipped cream all have an inflammatory effect.

Foods that combat inflammation are high in natural antioxidants and contain polyphenols, which are beneficial compounds found in plants. These include:

-- Dark leafy greens such as spinach, collard greens and kale

-- Vegetables such as cabbage and broccoli

-- Beans, which are high in fiber and antioxidants

-- Whole grains, which are high in fiber and help with inflammation

-- Protein sources that are high in omega-3 fatty acids, like salmon, mackerel, sardines and tuna

You don't have to completely cut out beef. But use it sparingly, more as a side dish rather than as the main event. Lose the sunflower, canola and corn oils and choose olive oil instead. Satisfy your sweet tooth with strawberries, cherries, raspberries, apples or blueberries. When you need a snack, swap out that bag of potato chips for a handful of almonds or walnuts.

While it's never too late to change your diet for the better, research here at UCLA suggests that it can't be done too soon. According to the findings of a recent study, women who ate a diet high in inflammatory foods during their adolescent years had a statistically greater risk of developing pre-menopausal breast cancer as adults. The thinking is that chronic inflammation associated with diet contributed to the increase in breast cancer risk.

The research into inflammation and diet has good news, too. Participants in a clinical trial at Ohio State University who ate an anti-inflammatory diet high in fish, fresh fruits and vegetables, and whole grains did better on bone density tests than did their chips- and sugar-eating counterparts.

How to move forward? There's no shortage of books and cookbooks devoted to anti-inflammatory eating. Grab your library card and hit the stacks -- the results will be both healthful and delicious.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)