Dear Doctor: How do I know if I have a penicillin allergy? I always tell doctors that, yes, I'm allergic to penicillin, because I think I remember a bad reaction from when I was a kid, but, honestly, I'm not sure. Does it even matter if I continue to avoid the penicillin family?

Dear Reader: Like all primary care physicians, we have a number of patients who check the "yes" box for penicillin allergies. It wasn't until we began a bit of background research into your interesting question, though, that we learned 10 percent of people in the United States think they're allergic to penicillin. But according to the Centers for Disease Control and Prevention, most of them are wrong. In fact, research shows that only 1 percent of the population in the U.S is truly allergic to penicillin. That means the chances that you're not actually allergic are high. (A bit more on that in a moment.)

Penicillin, which was discovered in 1928 and first came into general use in the 1940s, was heralded as a wonder drug. It was the first effective cure for bacterial infections ranging from earaches and sinus infections to strep, pneumonia and meningitis. Today the penicillin family of antibiotics, which are very targeted and quite affordable, remain the best treatment for a range of infections.

In addition, a recent study found that patients who were treated with broad-spectrum antibiotics because of a penicillin allergy had an increased risk of acquiring certain serious infections caused by antibiotic-resistant bacteria. So learning the truth about your suspected penicillin allergy is a good idea.

Symptoms of penicillin allergy include itching, rash, hives, wheezing, shortness of breath and fever. More severe is anaphylaxis, an acute allergic reaction that affects multiple body systems and can be life-threatening. Since some of these reactions can occur for reasons other than a dose of penicillin, you need to see an allergy specialist for a skin test that can give you a definitive answer. It typically begins with a check of your skin's reaction to a drop of a saline solution, which should not cause a reaction, and a drop of a histamine solution, which should cause itching and swelling similar to a mosquito bite. If your skin fails to react to the saline, but does react to the histamine, it means that you're able to react to a potential allergen. If your skin reacts to the saline, though, that means your skin is so sensitive that a test of potential allergens can't be accurately interpreted.

To test for a penicillin allergy, a drop of the antibiotic is placed on the skin, which is then scratched to allow penetration. If there is no reaction, this is followed by a small amount of penicillin being injected under the skin. If both of these tests are negative, a challenge dose of penicillin is administered to verify the results. If it turns out that you're one of the few who is truly allergic to penicillin, always let medical personnel know, and get a medical alert bracelet that identifies your drug allergy. Should your allergy be severe, carry emergency epinephrine in case of anaphylaxis or other severe reactions.

(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: Just how much of a role do personality traits have in determining how long someone will live? Recent news reports have suggested that they're important, but the explanation didn't really make that much sense to me.

Dear Reader: The idea that the way we view or interact with the world around us can affect our health is an intriguing one, and several studies have taken on the topic over the years. Since we're not sure which of these you're referring to, we'll look at a couple of the most recent ones.

Researchers in Italy who studied a group of 29 elderly men and women aged between 90 and 101 said their findings suggest that mental outlook plays a significant role in well-being. This is a departure from other approaches to the topic of longevity, which have focused on genetics. Despite the typical health issues you would expect to see among individuals of this advanced age, the subjects of the study were found to have more self-confidence than their younger relatives, who were also included in the study.

Using questionnaires and interviews, the researchers concluded that the elderly group, who had more positive feelings about their lives than their younger relatives did, exerted greater control over their lives and surroundings. They achieved this by being stubborn and domineering, personality traits that the researchers tied to their longevity. They also had strong ties to family, to their homes and land, and to their spiritual practices.

Thanks to this blend of resilience and optimism, the group of elders appeared to have struck a balance that helped them weather the many challenges they faced over the decades. And while lifestyle factors like diet and exercise were not the focus of this particular study, the researchers agreed that they are also quite likely to play a role.

Another study, this one based in England, analyzed the health and lifestyle data of 500,000 individuals ranging in age from 37 to 73. The researchers wondered whether being neurotic would have an effect on the length of an individual's lifespan. When they looked at the broad category of neurosis, they found a "weak correlation" between being neurotic and a shorter lifespan.

However, when they separated the data into sub-categories, they got a surprise. It turned out that neurotic individuals who self-reported their health as either fair or poor actually had longer lifespans. Neurotic individuals who said they were in good or excellent health didn't get the same boost to longevity. In this study, the conclusion was not that the neuroses themselves extended an individual's life. Instead, the personality traits associated with being neurotic led people to be more aware of their aches and pains, and to be more aggressive in seeking medical care. With more frequent assessments and screenings, serious conditions such as cancer or cardiovascular disease would be caught earlier and would thus be more responsive to treatment.

For those of us who are neither neurotic nor 90-year-olds living in rural Italy, there are still useful takeaways from the studies: Have regular medical checkups, be vigilant about basic screenings, and strive for a positive outlook even in trying times.

(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.)

Hello, dear readers, and welcome to autumn! You've been keeping our mailboxes full, so let's dive right in.

Cannabidiol, or CBD, one of several hundred compounds found in cannabis, continues to generate interest. Research has shown CBD to have analgesic and anti-inflammatory properties, and the FDA recently approved the first CBD-based epilepsy drug. We heard from a reader in Pennsylvania who uses CBD for pain and inflammation. He asked us to make clear that one can buy CBD extracted from hemp. "I have 19 broken bones and three bulging discs, and I haven't felt this normal in 12 years," he wrote. "I am a believer in hemp CBD."

Hemp contains virtually no THC, which is the psychoactive compound in marijuana. However, it's a close cousin to marijuana and remains in a legal gray zone in several states. The good news for CBD users is that several senators are working on legislation to make hemp products legal throughout the United States.

After a recent column about sunscreen, a reader asked us to point out that babies need special sunscreens that are different from those used by adults.

Infant sunscreens consist of mineral blockers, like zinc oxide or titanium dioxide. Adult sunscreens contain chemical additives that are not suitable for babies' delicate and sensitive skin. It's generally agreed that sunscreen use should begin at about 6 months of age. Until then, protect your baby from the sun with physical barriers like blankets, hats and umbrellas.

A column that referred to the anti-inflammatory properties of fish oil supplements for individuals with rheumatoid arthritis led a reader in Ventura, California, to wonder whether flaxseed oil could deliver the same results. Of the three main types of omega-3 fatty acids derived from foods and used by the body, flaxseed oil contains one, which is alpha-linolenic acid, or ALA. Although our bodies can convert ALA to the other two types of long-chain fatty acids (EPA and DHA) that render benefits, the degree of success relies on the presence of specific vitamins and minerals, as well as a genetically controlled enzyme process.

Bottom line: Yes, flaxseed oil will provide all the ALA you need. But due to the conversion factor of the remaining two omega-3's, it's not considered to be an even exchange for fish-based oils.

A reader from Louisiana who experiences "hanger," the irritability that can accompany a drop in blood glucose, thinks our column fell short of the mark. "Perhaps the answer could have included suggestions about what snacks would be helpful to the daughter in maintaining an appropriate sugar balance," she wrote. "The only level of control I have found that works is being able to eat the right foods on a more frequent basis than the average person."

Point well taken. If hanger is a part of your or a loved one's life, plan ahead with protein-based snacks like nuts or nut butters, cheeses or a protein bar. Do include complex carbs like fruit, veggies, legumes and whole grains. Don't reach for candy or other simple carbs, as they'll send the blood glucose roller coaster into overdrive.

(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.)