Dear Doctor: What can you tell me about an allergy to nickel? I recently had skin testing after experiencing itchy skin, a rash and fluid-filled blisters that several doctors thought might be mosquito-related. Instead, I tested positive for nickel allergy. Even the nickel in my bra clasps and earrings make me break out. Do I need to avoid certain foods? Is this problem hereditary?

Dear Reader: Nickel allergies are quite common. Although nickel is only about .009 percent of the Earth's crust, the metal and its compounds are found in a large number of common objects, such as coins, earrings, rings, watches, bras, belt buckles, mobile phones, medical devices and dental implants. And, as you referenced, nickel is found in small amounts in many foods. Unfortunately, nickel is the most common metal allergy in humans, affecting more than 10 percent of people in the United States. Women are five times more likely to have an allergic reaction to nickel than are men, largely because of their exposure to nickel-containing jewelry.

For people with nickel allergies, nickel ions provoke an immune response within the skin. After multiple exposures, the immune system can overreact when exposed to the metal. This type of reaction is called a delayed hypersensitivity reaction and it occurs 48 to 72 hours after the exposure.

There does appear to be some genetic predisposition to nickel allergies, but really, allergies to nickel are more related to exposure than to heredity. People who frequently handle coins, such as cashiers and toll road collectors, have greater amounts of allergic reactions on the hand than does the general population.

Again, the problem with nickel is how commonly the metal is used in clothing and in jewelry. That can be attributed to its strength and its resistance to oxidation. That said, Denmark has regulated nickel in its consumer goods and thus has the lowest rates of nickel allergy among industrialized countries. Other European countries have taken similar action; the United States has not.

Obviously, the best course of action is to avoid nickel in clothing and jewelry. One way to detect nickel is through a rapid testing kit, or dimethylglyoxime test. Here's how it works: You apply the test solution to a cotton swab, rub the swab on the metal of a product you're thinking of buying and -- if the product contains any nickel -- the swab turns pink.

Titanium, platinum, sterling silver, some types of stainless steel and gold that is at least 18 karats should be free from nickel. As for earrings with nickel (a common metal in such jewelry), you can create a barrier between it and your skin by coating the metal that touches your ear with nail polish or specific products marketed for nickel allergies. For clothing with nickel-containing buttons, you can apply an iron-on cloth over the metal portion or simply use duct tape. Finally, you can use barrier creams on the skin that comes in contact with nickel from jewelry.

Case reports suggest that skin reactions to nickel can diminish with a reduction of nickel in the diet, but your reaction appears to be related specifically to skin contact. So, for you, if you can't avoid nickel, I recommend using a barrier against it.

(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: It seems like every time I turn on the news someone's freaking out about ticks and mosquitoes. Haven't they always been around? What's with the alarm bells all of a sudden?

Dear Reader: The reason you're hearing so much about ticks and mosquitoes these days is because of a worrisome spike in the number of people becoming infected with the range of diseases these creatures cause. (We can't say "insects" because, while mosquitoes do fall into that category, ticks don't. They're actually arachnids -- like mites, spiders and their larger cousin, the scorpion.) According to a report released by the federal Centers for Disease Control and Prevention in May, the incidence of disease spread by ticks and mosquitoes has more than tripled between 2004 and 2016.

In just 13 years, the number of tick- and mosquito-borne illnesses in the United States has ballooned from 27,388 reported cases in 2004 to 96,075 reported cases in 2016. Even more concerning is the fact that more than half of that increase occurred between 2015 and 2016. And the key word here is "reported." Not every tick- or mosquito-borne illness is identified or gets reported, so the number of people made ill by a tick or mosquito bite is quite likely higher. (The CDC's report also covers fleas, with a total of 89 reported cases of plague over the 13 years of the report.)

Lyme disease accounted for 82 percent of the increase in tick-borne illness, according to the report. A closer reading of a breakout of the data reveals some troubling trends. For example, babesiosis, a malaria-like illness carried by deer ticks, went from zero cases in 2010 to more than 1,900 reported cases in 2016. Anaplasmosis, also caused by a bacterium carried by the deer tick, jumped more than 650 percent, from 875 cases in 2004 to 5,750 cases in 2016. If left untreated, the disease can cause internal bleeding, difficulty breathing, neurological problems and kidney failure.

When it comes to mosquitoes, the report offers both good and bad news. Cases of Zika have gone from zero in 2015 to 41,680 the following year. Virtually all were reported in Puerto Rico, American Samoa and the U.S. Virgin Islands. West Nile virus, meanwhile, which hit a high of 5,674 cases in 2012, dropped by half by 2016. In addition, the CDC reports that nine new germs that are spread by ticks and mosquitoes have been identified since 2004. Scientists say the rise in disease rates, as well as the widening of their geographic scope, is due in part to the warming climate, which expands the pests' habitats. Global trade and travel also play a role.

Our aim here is not to alarm, but to stress the importance of vigilance in protecting yourself and your family. Bottom line: Create a barrier between yourself and the potential threats. That means appropriate clothing to cover you when spending time outdoors, bug repellent for a chemical shield, and regular visual checks of your skin, scalp and clothing. And don't forget about the pets -- a range of excellent meds are available to keep your furry companions tick- and flea-free as well.

(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: Does Oscillococcinum work as a flu treatment?

Dear Reader: Oscillococcinum is a homeopathic preparation. Unlike the sound of the name, it has nothing to do with bacteria. The product is derived from wild ducks' hearts and livers. In a homeopathic method, that extract is diluted up to 200 times, such that a miniscule amount of the material is in the final product. The belief is that the heart and liver of a wild duck may have influenza virus and that diluting this material may somehow cause an increased immune response to the flu.

But no studies have shown that Oscillococcinum causes any specific alteration to the influenza virus or the immune system.

However, studies have looked at Oscillococcinum for the prevention and treatment of influenza. A 2015 study reviewed six trials. Two trials assessed the use of Oscillococcinum for prevention of influenza and four trials assessed its use for treatment. The two prevention trials, with a total of 327 people, found a 52 percent decrease in influenza risk among those who used Oscillococcinum.

Out of the four treatment trials, two of the trials -- with a total of 796 participants -- found an 86 percent greater chance that symptoms would resolve after 48 hours among those who took Oscillococcinum compared to those who didn't. (This isn't a dramatic difference when you consider the absolute numbers. To be precise, it amounts to a 16.7 percent chance of resolution in the Oscillococcinum group and a 9 percent chance of resolution in the placebo group.) One interesting note is that patients ages 12 to 29 were much more likely to report a positive effect than those over 30.

After three days, however, the difference between the placebo group and the treatment group declined, and by the fourth day there was no difference. Of further note, there was a 39 percent reduction in the use of other influenza medications in the group that took Oscillococcinum.

The two other studies in this review looked at a physician assessment of patients 48 hours after the onset of symptoms, and while there was a mild improvement seen with the preparation, it was not statistically significant.

Note that the authors of the review found multiple flaws in the methodology of the studies and said that the studies were potentially biased. Thus, they were not convinced of the benefits of Oscillococcinum for either the prevention or treatment of influenza.

A 2009 and 2012 review of multiple studies showed a mild benefit toward Oscillococcinum, but these studies also were considered of poor quality, and the authors could not make any conclusion about the benefit of the medication.

As for whether Oscillococcinum works, I know it isn't satisfactory, but the answer is "maybe." Better-quality studies are necessary. One good thing about the prior studies was that there was little difference between the medication and placebo regarding side effects, so if you take it, it should be safe.

(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.)