Dear Doctor: My pharmacist recently told me I could get a flu shot, even though I have an egg allergy. Is this true?

Dear Reader: You're smart to ask, especially now. As the current flu season illustrates, the influenza virus accounts for thousands of illnesses and deaths each year. The number of deaths attributed to influenza over the past 40 years has ranged from 3,349 to 56,000 a year; the average annual death rate is about 23,000.

Traditionally, and for the majority of flu shots, the influenza virus is created by injecting it into fertilized chicken eggs, where it multiplies. The fluid within the egg is eventually removed, inactivated and used for the injectable vaccine. Although this fluid is saturated with the virus, it also contains egg protein. That's potentially a problem because many people are allergic to eggs, with up to 2 percent of American children having egg allergies. Some of these allergies manifest as hives, but others are life-threatening, with severe shortness of breath and a rapid decline of blood pressure (called an anaphylactic reaction).

Thus, the primary worry about the use of eggs to make the vaccine has been that the vaccine could lead to major allergic reactions. Four people died of anaphylactic reactions after receiving the influenza vaccine between 1990 and 2005. (Whether these four people had an allergy to eggs is unknown.)

Because of the risk, manufacturers for years have been trying to reduce the amount of egg protein within the vaccine -- and they've succeeded. Inactivated flu vaccines are supposed to contain less than 1 microgram of egg protein per dose, but the protein content of vaccines has been measured to be significantly lower than this. Testing of the 2010 and 2011 influenza vaccines, for example, found the level to be 0.17 microgram of egg protein per dose of vaccine.

Multiple studies have assessed the impact of giving the flu vaccine to people with egg allergies; some of the vaccines included up to 0.7 microgram of egg protein per dose given. Overall, these studies identified no anaphylactic reactions. One study did show that, in people with egg allergies, about 1 in 100 people experienced minor allergic reactions, which were treated with an antihistamine. Most notable perhaps is that people with a history of anaphylactic reactions to egg did not have reactions when given the vaccine.

Based on this data, both the Centers for Disease Control and Prevention and the American Academy of Pediatrics have stated that the vaccine can be given to people with egg allergies of any severity. They suggest, however, that to address the theoretical possibility of a severe reaction, people giving the vaccine should have medications and resuscitative equipment on hand.

So, yes, your pharmacist was right: Even if you have egg allergies, the flu vaccine is safe. Personally, I'd like to know the concentration of egg protein in any given vaccine (they're made by various manufacturers), with those with lower concentrations given to people with egg allergies. Perhaps that data will come.

For now, if you have a severe allergy to eggs and can't shake your concern about the flu vaccines produced from eggs, you can choose between two that do not require eggs for production. This is also an option if you've had minor reactions to the flu shot in the past.

Regardless of whether you opt for the traditional vaccine (I would) or choose an alternative, the important thing is to get vaccinated. It will reduce your likelihood of severe illness and death.

(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: When our first son was born, we almost lost our minds as we rode out his bouts of colic. Our second son is due this spring and the idea of dealing with colic again already has me panicking. I've been reading that certain probiotics can help. Is this true?

Dear Reader: We honestly think it's a toss-up as to who suffers more when an infant is caught in a bout of colic -- the baby or those trying to help him. For anyone fortunate enough to not know what we're talking about here, colic is a condition in which a baby has regular, often predictable, episodes of intense crying that last anywhere from several minutes to several hours. It typically begins when the baby is a few weeks old and can continue for several months.

The frustrating thing is that the child can be well-fed, well-rested, in a clean diaper and in a comfortable environment. Then suddenly she or he will be in profound and prolonged distress. The crying is often high-pitched, accompanied by clenched fists, tensed-up stomach muscles and a defensive, curled-up posture. The level of discomfort is such that comforting a colicky baby can seem all but impossible.

A new study has good news for parents of colicky babies. It appears that a certain probiotic that is already being marketed as a treatment for colic can, in fact, be effective. Known as Lactobacillus reuteri, this species of probiotic has been shown to exhibit antimicrobial activity. And while various small studies have already pointed to Lactobacillus reuteri as a hedge against colic, this latest study backs up the claim for the probiotic with a larger and broader sample size.

Researchers looked at the raw data collected from babies who had been enrolled in four different clinical trials. The stated purpose of these clinical trials had been whether Lactobacillus reuteri was effective in reducing the distress of colicky babies. In these trials, half of the infants with colic received the probiotic, and half received a placebo. The babies were then monitored for outcomes that included how long each baby spent crying during a bout of colic, the degree of fussing that took place, and whether or not the colic symptoms had resolved after three weeks of treatment.

According to the findings, the group taking the probiotic spent measurably less time less crying and fussing than did the babies in the group that received the placebo group. But -- and this is important -- researchers were only able to confirm the positive effect of the probiotic among babies who were exclusively breast-fed. This was because there were not enough formula-fed infants in the clinical trials to generate sufficient data from which to draw conclusions.

The bottom line: This is a promising avenue of treatment for breast-fed babies with colic. We suggest that parents who want to give it a try (Lactobacillus reuteri is widely available as an over-the-counter product) do so in partnership with their pediatricians.

(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 you shed some light on transient global amnesia? I was diagnosed with this five years ago (I'm now 71) after my family noticed that I couldn't recall common facts. I had no physical ailment or injury prior to this, and I'm told that the recurrence rate is 1 percent.

Dear Reader: Transient global amnesia is, as the name describes, a short-lived inability to retain new memories. Because the episodes are so sudden, they can be disorienting to all involved. Afflicted people often repeatedly ask questions about the date, their location or their reason for being there. They can temporarily lose memories from a few hours before the event to, more rarely, up to a year before the event.

Note that such episodes do not affect a person's ability to perform complex tasks such as driving, cooking, lecturing and playing a musical instrument. Nor do the events interfere with self-awareness.

The episodes last, on average, about six hours, but can be as short as one hour or as long as 10 hours. Afterward, a person does not remember anything that transpired during the episode and may even lose some memories formed just before the incident. Although the episodes can be preceded by an acute emotional event, physical activity, or exposure to cold or heat, doctors don't really know what causes such amnesia.

MRIs have shown that the events affect the memory centers of the brain in the temporal lobe and in the hippocampus. Like the symptoms, however, the resulting lesions that develop in these areas are not permanent. Some brain experts suspect that blood flow restriction may be a trigger, but the evidence for this is thin. Another hypothesis, which has more merit, is that a backflow of venous blood is the catalyst; such flows are more likely to affect the aforementioned parts of the brain.

One strong risk factor is psychogenic stress -- in other words, a psychiatric condition that produces a physical response. A 2005 study found that people with a history of psychiatric disease or alcohol abuse had three times the likelihood of experiencing transient global amnesia.

The condition typically occurs in people ages 50 to 80 and is diagnosed in one in every 3,500 people over 50 each year in the United States. The peak incidence occurs in those 60 to 65. Men and women are equally affected. Because the symptoms can resemble those of a stroke or a transient ischemic attack, many people mistake the condition for a stroke or TIA. Unlike those conditions, however, transient global amnesia doesn't have a vascular cause, and people who experience it have the same incidence of stroke as the general population. Nonetheless, because of the similarity in symptoms, immediate medical attention is needed to rule out more serious causes.

You mention a 1 percent recurrence rate, but studies have shown the rate to be about 5 percent. This is still very low.

This sudden loss of memory must have been unnerving for you. Please take some comfort in the fact that it's unlikely to happen again.

(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.)