When you suspect your child has a fever, you want a thermometer that’s easy to use and offers an accurate reading. But with so many options available, picking the best device can be confusing. Should you buy an ear thermometer or an oral one? Will a forehead thermometer offer a reliable reading on infants?

“Choosing the best thermometer is really dependent on the age of your child,” says Christopher Vlasses, MD, a hospitalist at UCSF Benioff Children’s Hospital in Oakland, California. “Overall, digital thermometers are still considered the best option in terms of cost, ease of use and availability.”

If you’re in the market for a new family thermometer, consider this advice.

Accurate styles

Digital stick thermometers. “These thermometers can be used orally, rectally and axillary (under the arm),” Vlasses says. “They are cost effective and give the most accurate readings.”

Rectal thermometers. “For best results in babies and toddlers up to three years of age, the American Academy of Pediatrics (AAP) recommends using a digital rectal thermometer,” Vlasses says.

While some parents worry about the baby’s comfort, AAP recommends applying a little petroleum jelly to a digital rectal thermometer, putting your baby on his back on a changing table and lifting his legs as if you are going to change a diaper.

“If your child is under six months old, slide the thermometer about half an inch into their rectum and hold in place until the thermometer signals it’s done — usually about two minutes,” Vlasses says. “If your child is older than six months, you can slide the thermometer about an inch into their rectum. Always be sure to clean the thermometer with soap and water or rubbing alcohol afterwards and make sure to label the thermometer used to take rectal temperatures so it is never to take an oral temperature.”

Oral thermometers. Often by the time your child turns four, Vlasses says she should feel comfortable holding a digital oral thermometer under her tongue. Place the tip of the thermometer under your child’s tongue in the back of her mouth and ask her to keep her mouth closed until the thermometer signals it’s done. “If your child has had something to eat or drink, wait 30 minutes before taking their temperature orally in order to get an accurate reading,” Vlasses says.

Ear thermometers. Vlasses says that an ear thermometer also can be a good option for older children, though if your child has earwax or you’re not consistent in how you position it in his ear, the thermometer may give a low or otherwise inaccurate reading. To use an ear thermometer, parents should gently pull the ear straight back and hold the child’s head so it doesn’t move. Some of the newer ear thermometers feature a guidance system that confirms with a light and a beep when a parent has taken a good measurement and alerts you when the thermometer has not been inserted properly.

Forehead thermometers. To use these handy gadgets (also known as temporal thermometers), parents simply swipe the thermometer across their child’s forehead. The device measures the temperature of the skin over the temporal artery, a major artery connected to the heart. These thermometers can be used on kids ages three months and older, as well as older family members. A study published in the September 2012 issue of the American Journal of Critical Care found that temporal artery thermometers and oral thermometers registered temperatures more accurately than other noninvasive methods.

Still relatively new, temporal thermometers are the most expensive option at $30 to $50, notes Vlasses..

Less-accurate styles

Forehead strips. These press-on strips are billed as effective and inexpensive. But because of accuracy issues, the AAP recommends against them.

Armpit thermometers. “These types of thermometers tend to be less accurate,” Vlasses says. “If your child is less than 3 months and an ancillary [armpit] thermometer shows they have a temp over 99.0, it’s best to confirm that they have a fever by taking their temp with a rectal thermometer.” To use this type of thermomter, place the tip of a digital thermometer under your child’s arm, then have her fold her arm across her chest to hold the thermometer in place until you hear it beep.

Pacifier thermometers. While using a thermometer shaped like a baby’s pacifier sounds like a great idea, Vlasses says these don’t always offer an accurate reading. He notes the AAP doesn’t recommend them. To use one, your little one sucks on the thermometer until it beeps.

Downright dangerous

Mercury thermometers. “These types of thermometers that were used years ago are no longer recommended,” Vlasses says. “The AAP urges parents not to use glass mercury thermometers due to safety issues with mercury and broken glass. If you still have one of these thermometers, ask your health care provider how to dispose of it.”

What’s a fever?

The AAP says a normal temperature for a healthy baby is between 97 and 100.4 degrees F. If your baby has a rectal temp of 100.4 or higher, you should notify your pediatrician. Any fever in a baby under three months of age should be reported to the doctor, as well as a fever higher than 104 F in older children.

Linda Childers is a mom, pet-owner and California-based health writer.