Dear Doctor: I recently read about a woman who lost a leg from toxic shock syndrome and might lose another one. How is this possible? I thought toxic shock was related to using tampons.

Dear Reader: Toxic shock syndrome is a rare but potentially fatal illness in which toxins produced by certain bacteria cause an immune response that is so powerful, it becomes life-threatening. And although toxic shock syndrome first made headlines in the late '70s and early '80s, when it caused the deaths of hundreds of women who used superabsorbent tampons that were left in place for many hours, the fact is that it can develop in people of any sex and any age.

Most often, toxic shock syndrome is a reaction to the toxins produced by Staphylococcus aureus -- also referred to as staph -- bacteria. (Although it can also be triggered by group A streptococcus, or strep bacteria, that is less frequent.) The S. aureus bacterium, one of the most common agents of infection in humans, can enter the body through cuts, burns or recent surgery. It causes urinary tract infections, pneumonia, gastroenteritis, meningitis, septic arthritis and a host of skin infections. In toxic shock syndrome, the bacteria produce small proteins known as superantigens, which rev up the immune system to a dangerous degree. The resulting response is so powerful that the body goes into shock.

Symptoms include high fever, a dangerous drop in blood pressure, vomiting or diarrhea, mental confusion, headache, profound fatigue or unconsciousness, and a cascade of organ failure. One of the earliest symptoms can be a sunburnlike rash that appears on the palms of the hands, soles of the feet, the lips and mouth, or the eyes. It's an extremely grave condition that often requires hospitalization for supportive care to help with breathing, liver and kidney function and blood pressure. Source control of the infection is crucial to recovery.

Because the vagina is a warm, moist environment, tampons, diaphragms, menstrual cups and menstrual sponges can all provide a medium on which bacteria can grow and proliferate. The surge of toxic shock cases 40 years ago was tied to a specific brand of superabsorbent tampon that was shaped like a cup. Due to a certain chemical additive, it was advertised to be able to hold 20 times its own weight of liquid. The idea was you could leave a single tampon in place for days. The result was basically an internal petri dish, primed for dangerous bacteria to flourish.

With a change to tampon materials, as well as warnings against leaving them in place for more than eight hours, cases of menstrual-related toxic shock have dropped to about one per 100,000 people. By contrast, between 1979 and 1996, there were 5,296 reported cases. To protect yourself, choose the low-absorbency tampons and change them every six to eight hours. Safest of all, skip tampons altogether. And if you experience any of the symptoms associated with toxic shock, seek medical care immediately.

(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: I just learned that the constant pain in my right knee, which I injured playing college basketball, is osteoarthritis. I'm only 33 and want to do everything I can to get better. Is it true that fish oil can help? Is there anything else I can do?

Dear Reader: Osteoarthritis, also referred to as OA, is a chronic degenerative condition that affects the joints. Unlike rheumatoid arthritis, which is an autoimmune disease, osteoarthritis is associated with the breakdown of the cartilage in the joints due, in large part, to wear and tear. Although OA is most common among people in their mid-60s and older, it can affect people of any age. A sports injury like yours is a significant risk factor for developing OA. So are chronic overuse, being overweight or obese, and genes. Both types of arthritis tend to be more common in women than in men.

OA most often affects the weight-bearing joints of the knees and hips. It can also affect the neck, spine, shoulders, elbows, hands and feet. Symptoms include joint stiffness, swelling, a reduced range of motion and pain. People with OA often report hearing clicking or popping sounds when they bend their joints. One side of the body is usually affected more than the other, perhaps because we tend to have a "stronger" side and unconsciously allow it to do more work.

Morning stiffness is a challenge and can require a half-hour or so of slow and deliberate activity to get the affected joints working freely. That stiffness typically returns after long periods of inactivity, like sitting at a desk at work, or remaining in the same position for extended period of times, such as when driving. Diagnosis is done through imaging tests like MRIs or X-rays, which can show the extent of damage that has taken place to the joint capsules.

With the findings from a recent study published in the journal Rheumatology, researchers from Great Britain added to the mounting evidence that nutrition and exercise play a role in managing the disease. An analysis of 68 studies about OA found that patients who took a low-dose supplement of fish oil of 1.5 capsules per day reported a measurable reduction of pain. The thinking is that the essential fatty acids in the fish oil help address the chronic inflammation that is part of the OA disease process.

Also important to managing OA was weight loss, which not only eased pressure on the joints but also led to a reduction in inflammation. In addition to a healthful diet of whole foods to reduce blood lipid levels, vitamin K, which is present in abundance in kale and spinach, was associated with positive outcomes. Vitamin K is required for the synthesis of certain proteins that help maintain the health of bones and connective tissues.

Finally -- and this can seem counterintuitive when dealing with the pain and stiffness of OA -- a gentle but consistent program of aerobic exercise, along with strength and flexibility training, proved to be important. None of this is a cure, but when undertaken together and incorporated into an ongoing lifestyle, living with OA can be a bit easier.

(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: I have some dark chocolate every day and my (otherwise kind and loving) husband teases me for believing the news stories that chocolate is good for you. Please tell me that I haven't fallen for a bunch of quack science!

Dear Doctor: We can certainly understand how the idea that chocolate offers health benefits might spark a bit of skepticism. After all, when we hear about so-called superfoods, it's foods like kale, fish oil or green tea that tend to top the list. The idea that something as delicious as chocolate might be anything more than an indulgence takes a bit of getting used to. And yet you're right -- a number of studies have linked chocolate with a range of positive outcomes. The results of recent research suggest that chocolate improves memory and brain function, lowers blood pressure and cholesterol, can boost immunity and has a positive effect on mood.

But before you unwrap a chocolate bar in celebration, there's an important caveat. It's only dark chocolate that confers these positive effects. That is, chocolate with a minimum cacao concentration of 70 percent. That's because cacao is rich in chemical substances known as flavanols, which have potent antioxidant properties. Studies have shown that flavanols have a positive effect on connections between brain cells, offer protection from toxins and can shield the body from some of the damaging effects of inflammation.

The catch here is that in its pure state, cacao is relentlessly bitter. It's the sugar and fat that get added during manufacturing that give chocolate its sweetness and silky-smooth feel. For many people, the high levels of cacao needed for chocolate to become potentially beneficial render it unpalatable. If you're a lover of dark chocolate, though, you're in luck.

The results of two recent studies regarding dark chocolate, which were presented at the Experimental Biology 2018 annual meeting last April, back up many of the existing health claims about dark chocolate. (They also give you some recent data to use the next time you get teased for your chocolate-loving ways.) Researchers from Loma Linda University examined the brain scans of study participants before and after they ate 48 grams -- that's 1.7 ounces -- of dark chocolate. In the post-chocolate scans, they saw increased activity among certain immune cells in functions like T-cell activation, cellular immune response and in genes involved in neural signaling. That translates to beneficial effects on mood, memory, stress levels and inflammation. As with all studies that have a fairly small sample size, the findings here need further investigation to nail down the cause-and-effect of what the researchers saw.

Meanwhile, when you do eat chocolate, be sure to go for 70 percent cacao or higher. Natural chocolate has more flavanols than Dutch process, which uses alkali to neutralize the acid found in cacao. This makes it tastier, but also lowers the flavanol content. And remember that despite all of its potential health benefits, chocolate is also delivering both fat and calories. Be sure to adjust your diet accordingly.

(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.)