Dear Doctor: I am an 86-year-old female, and sometimes, about an hour after eating a meal, my blood pressure drops significantly, from a normal of 123/74 to as low as 93/47. When it happens, my lips tingle and get dry, and I feel "zonked" out, like I'm in some kind of a trance. What causes this? What can I do?

Dear Reader: What you've described is known as postprandial hypotension, which means that someone's blood pressure drops measurably in response to eating. (Postprandial refers to the time after a meal, and the "hypo" in hypotension refers to low blood pressure.) The condition is common in older adults and is estimated to be present to some degree in up to 30 to 40 percent of the elderly. It is also often found in people living with Parkinson's disease. Because the condition can lead to dizziness, falls and fainting, and in some cases can result in angina, stroke or heart attack, it's important that it be diagnosed and addressed.

Each time we eat, we require our circulatory system to reorganize and recalibrate its activities. That's because the tasks of digestion and absorption create the need for additional blood flow to the stomach, particularly the small intestine. To accommodate that need, blood vessels throughout the body that are not involved in the digestive system begin to narrow. This allows blood to be redirected to the stomach and small intestine, while still maintaining consistent blood pressure throughout the body. To aid in those dual goals, the heart beats faster. As the stomach and intestines complete their work, blood vessels dilate again, and the heartbeat returns to normal.

In people with postprandial hypotension, blood flows as needed to the digestive organs. However, the circulatory system doesn't respond with the appropriate measures. For reasons that aren't yet clear, the heart rate doesn't increase enough, and blood vessels do not narrow enough to compensate for the redirected blood flow. That results in a drop in blood pressure and the symptoms you described.

Since low blood pressure can lead to a loss of consciousness and a fall, as well as the more serious complications we mentioned earlier, it's important that you address this with your family doctor. It sounds as though you've been tracking your blood pressure with a home monitor, and your doctor will want to see those readings. She or he will also want to follow up with a definitive diagnosis, which entails a baseline blood pressure reading before a meal, and then up to two hours of post-meal blood pressure monitoring.

People who take blood pressure medications may be asked to make changes to how and when they take the drug. But please don't make any changes without your physician's input.

Lifestyle changes may include a pre-meal cup of coffee, as caffeine can cause an increase in blood pressure. A large glass of water before a meal has also been shown to be helpful. Diet may play a role too, as postprandial hypotension has been linked to meals high in carbohydrates. It's a good idea to track what you're eating and see if the food correlates to episodes of low blood pressure.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My 5-year-old nephew has a severe peanut allergy. It's so bad that he can't risk eating anything that isn't prepared by the family. Even the highly supervised snack time at school isn't safe. Now I've read about a new peanut allergy drug that is an oral immunotherapy. How does it work? Do you think it could help him?

Dear Reader: We are parents as well as physicians, so we understand the nonstop vigilance that comes with a food allergy. But peanuts are common enough that, despite a family's best efforts, it's likely a child with a peanut allergy will come into contact with them at some point. That's why the potential of the new immunotherapy drug you mentioned is so exciting. Not only does it offer people with peanut allergies a new measure of protection, it opens up a range of possibilities for future allergy therapies.

The new drug, currently known as AR101, is under review by the Food and Drug Administration. This follows the completion of a series of clinical trials in the efficacy and safety of the drug. AR101 works by very gradually exposing an individual to peanut proteins, which desensitizes the immune system. This takes place over the course of six months, during which the peanut content in the daily oral dose is methodically increased. At the end of a year -- six months of treatment followed by six months of maintenance -- 67 percent of the children in the study were able to safely eat two peanuts. Researchers have made it clear that the goal is not to cure the allergy, but to reduce the severity of symptoms should accidental exposure to peanuts ever take place.

Unfortunately, the drug didn't work for everyone. More than 10 percent of the participants exited the study before it was complete due to adverse reactions. Of those who remained, 14 percent required intervention with epinephrine, which eases symptoms. The bad news for adults living with a peanut allergy is that the treatment was not effective in those adults who were enrolled in the clinical trials.

For those who aren't aware, peanut allergy is one of the most common causes of severe allergy attacks in children. A reaction can be triggered by even a tiny amount of the legume, and symptoms range from mild to severe. They include runny nose, itching or tingling in the mouth and throat, hives or other skin reactions, gastric distress like nausea, vomiting or diarrhea, and respiratory issues like wheezing, shortness of breath or a tightening of the throat. At its most severe, a peanut allergy can cause anaphylaxis, a life-threatening reaction that is causing an increasing number of hospitalizations. Symptoms include swollen airways that prevent breathing, a precipitous drop in blood pressure and loss of consciousness.

A challenge of the treatment is that after receiving each daily dose of the medication, children have to rest for two hours but cannot sleep during that time. Still, physicians and researchers are buoyed by the results. AR101 has been flagged by the FDA as a breakthrough therapy, which makes it eligible for a swift approval process. If all goes well, the manufacturer reports that the drug could be available by the end of 2019.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I've noticed that after running, especially when I've really pushed myself, I'll cough for a while. A friend says it's something called exercise-induced asthma. Why is it happening?

Dear Reader: Your symptoms are in line with something known as exercise-induced bronchoconstriction, often referred to as exercise-induced asthma. It usually happens after -- but sometimes during -- exercise that's vigorous enough to significantly increase your heart rate and respiration. In some people, this post-exercise period of coughing is accompanied by additional symptoms like a tight chest, shortness of breath or wheezing. In the majority of cases, these symptoms prove to be temporary and breathing returns to normal.

Asthma is a chronic disease in which the airways to the lungs become narrowed or inflamed, which interferes with breathing. This inflammation often makes people with asthma sensitive to a range of factors, including dust, mold, tobacco smoke, pollen, pet dander, air pollution, chemicals, certain medications, exertion and cold air. Known as triggers, these sensitivities can cause an asthma attack in which the airways become even more inflamed and symptoms worsen. In severe cases, an asthma attack can cause airways to become fully obstructed and can be fatal.

Unlike people with asthma, who have multiple triggers, those with exercise-induced asthma experience symptoms only during or after exertion. Some find that their episodes are associated with exercising in air that is colder or dryer than normal. The same workouts that produce no symptoms in the warmer months may bring on coughing and wheezing when the weather turns cold, or when indoor heating takes the moisture out of the air. In most people, symptoms start five to 20 minutes after beginning to exercise, or five to 10 minutes after exertion has ended, and are short-lived.

Diagnosis of exercise-induced asthma typically begins with a resting lung function test. This is done with a breathing device known as a spirometer, which measures the volume of your inhale, the volume of your exhale and how quickly you expel the air from your lungs. This may be followed by an exercise challenge test, like running on a treadmill, riding a stationary bike or climbing stairs, in order to trigger symptoms. The exercise challenge ends with another spirometry test, which will reveal any changes in lung function.

Other conditions can have symptoms similar to those of exercise-induced asthma. These include allergies, chronic obstructive pulmonary disease (COPD), obesity, gastro-intestinal reflux, vocal cord disfunction, congestive heart failure and certain lung diseases. As a result, we think it would be wise to check in with your family doctor about what's happening.

Depending on his or her findings, your doctor may suggest using an asthma inhaler or bronchodilator prior to the start of exercise. Certain behaviors can help as well. Take time to warm up before exercise, as this can help lessen symptoms significantly. Infection plays a role in asthma symptoms, so don't exercise when you're sick. If you have allergies, take note of pollen counts. Keep tabs on symptoms and, if they get worse, see your doctor. The good news is that with proper management, people with exercise-induced asthma can safely stay active.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)