DEAR DR. ROACH: With the flu season coming on, would you please discuss the difference between what people call the “stomach flu” and what the flu really is? I have two friends who last year said they weren’t getting the flu shot anymore because despite having it, they got the flu. They each described several hours of throwing up, but feeling better the next day. I suggested that they probably had a gastrointestinal episode and not influenza, which is a respiratory disease. They insisted that they had the flu, and they’d always learned that the stomach flu is influenza and the flu shot is meant to prevent it. Since then I’ve spoken to two others who believe the same thing. This seems to be a relatively prevalent belief. -- G.C.
ANSWER: You are right that there is much confusion about what influenza is. Influenza typically begins with sudden onset of fever, headache, fatigue and severe body and muscle aches. Influenza occurs about two days after exposure. There also often are symptoms of cough, sore throat and nasal discharge, just as there are with the common cold, but the sudden onset, fever (commonly 100 to 104 degrees) and muscle aches help distinguish cold from flu.
Gastrointestinal symptoms -- such as nausea, vomiting and diarrhea -- are less common in influenza, and these symptoms in absence of the major manifestations listed above makes the diagnosis of flu very unlikely. In late fall through early spring, some diarrheal illnesses (mostly viral) are common, but you are correct that these are NOT influenza.
The flu shot contains viral proteins, not live influenza, and it is incapable of causing the flu. Many people will have a sore arm and sometimes mild fever and body aches after a flu shot. This is just part of the body’s reaction, and it goes away by itself within 24 hours. There is a live influenza vaccine given by nasal spray, which also generally has mild side effects. This may be given to adults under 50.
The flu shot is not perfect: You still can get the flu after receiving the shot. However, the flu shot is effective at reducing the most serious cases of flu, such as influenza pneumonia, which can be life-threatening or fatal.
DEAR DR. ROACH: Can you please explain how an MRI machine affects the pigment in a tattoo? My friend’s MRI procedure was stopped because she was experiencing a burning sensation at her lower eyelids, which had previously been tattooed with black ink. Does this happen only with black ink? Which colors are safer? -- J.H.
ANSWER: Reactions between the ink in tattoos and MRI scanners are well-documented in the literature. Some inks -- mostly black, red and brown -- are made with iron or titanium oxides. Only 1.5 percent of people with tattoos have reported bad experiences in MRI machines.
Iron and titanium oxides conduct electricity, and the strong magnetic field in an MRI scanner can cause a current to travel between different tattoos or different portions of a tattoo -- especially those with loops in the pattern. The electric current causes heat, and even can cause minor burns. Cold packs or ice placed on the area during MRI can minimize damage, but some MRI facilities will not perform an MRI on tattooed individuals, especially if the tattoo covers a large area.
If a magnet draws up the skin with a tattoo, then that area is at risk.