Written and maintained by CASRAI Editorial Board
Last updated
This page describes products and general use; it is not medical advice.
Short answer: an infant digital thermometer is an electronic clinical thermometer. What matters for a baby is where it reads (rectum, forehead, ear or armpit) and how its sensor works, because the American Academy of Pediatrics (AAP) ties each site to an age range. Who uses it: parents and caregivers, childcare and clinic staff, and the buyers who equip them.
What is an infant digital thermometer?
It is a battery-powered electronic thermometer used to measure a baby’s body temperature and show it on a digital display. The same product class covers contact models (read at a body site) and infrared models (read heat radiated from the skin or eardrum). For the generic device, see what a medical thermometer is.
Do digital thermometers work on infants?
Yes, but not every type suits every age. The AAP states that rectal temperatures are the most accurate, especially for infants under 3 months of age; that a temporal artery (forehead) thermometer can be used for all ages; and that a tympanic (ear) thermometer is for children age 6 months and older (AAP HealthyChildren, checked 2026-10-30).
Types of infant thermometer by reading site
| Type | What it reads | AAP statement on age and accuracy |
|---|---|---|
| Rectal (infant rectal thermometer) | Temperature in the rectum | Most accurate; best especially for infants under 3 months |
| Temporal artery (infant forehead thermometer) | Infrared heat from the blood vessel across the forehead | Can be used for all ages; the next most accurate |
| Tympanic (infant ear thermometer) | Infrared heat from the eardrum | Age 6 months and older; not reliable for younger babies because ear canals are too narrow |
| Armpit (axillary) | Skin temperature at the armpit | Least accurate; can screen any age |
| Oral | Temperature in the mouth | Not recommended until age 4 or older |
Source for every row: AAP HealthyChildren, “How to Take a Child’s Temperature”, checked 2026-10-30.
How does a forehead thermometer work?
A temporal artery thermometer measures infrared heat waves coming off the blood vessel that runs across the forehead just below the skin (AAP). It reads radiated heat, so nothing is inserted into the body.
What is the difference between temporal and tympanic thermometers?
Both are infrared thermometers, often sold as an infant infrared thermometer, but they read different places. A temporal thermometer reads the forehead blood vessel and the AAP says it can be used at all ages. A tympanic thermometer reads infrared heat from the eardrum; the AAP says it is not reliable for babies younger than 6 months because their ear canals are too narrow, that readings depend on placement, and that a child who has just been outdoors in the cold may give a low reading.
Regulatory class
In the United States, clinical electronic thermometers are regulated under 21 CFR 880.2910, named “Clinical Electronic Thermometer”, as Class II devices with product code FLL. An FDA 510(k) clearance letter for an infrared thermometer (FDA letter K201600, checked 2026-10-30) shows this classification and clearance as substantially equivalent through the 510(k) route. This is a classification fact, not a performance ranking.
How to choose
The only selection criterion this page states is the one the AAP states: match the measurement site to the child’s age. A tympanic model is outside the AAP’s stated age range for babies under 6 months, whereas rectal and temporal readings are described as suitable for infants. For staff stocking a first-aid or clinic area, a point-of-care diagnostic station and a childcare first-aid supply checklist show where thermometers sit among other supplies.
Safe use and handling basics
- Read the manufacturer’s instructions for use for the exact model; this page does not replace them.
- Do not use an oral thermometer on an infant; the AAP does not recommend oral readings before age 4.
- Questions about a baby’s temperature or health belong with a pediatric clinician.
- Older glass thermometers contain mercury; see mercury in thermometers.
Common mistakes
- Using an ear (tympanic) model on a baby under 6 months, outside the AAP’s stated range.
- Treating an armpit reading as equal to a rectal one; the AAP calls the armpit the least accurate site.
- Taking an ear reading right after the child was outdoors in the cold, which the AAP says may read low.
FAQ
Do digital thermometers work on infants?
Yes. Per the AAP, rectal and forehead (temporal artery) readings are suitable for infants, while ear readings are for children age 6 months and older.
What is the difference between temporal and tympanic thermometers?
Temporal reads the forehead blood vessel and suits all ages; tympanic reads the eardrum and suits age 6 months and older (AAP).
How does a forehead thermometer work?
It measures infrared heat from the blood vessel across the forehead just below the skin (AAP).
Sources
- American Academy of Pediatrics, HealthyChildren.org: How to Take a Child’s Temperature, checked 2026-10-30.
- FDA 510(k) clearance letter K201600 (infrared thermometer; 21 CFR 880.2910, Class II, product code FLL), checked 2026-10-30.
Related device: blood pressure cuffs.
