Babies teethe because their first set of 20 teeth, which began forming in the jawbone before birth, are pushing through the gums to prepare for solid food. The process typically starts around 6 months of age, when the lower front teeth break through, and continues until roughly age 3. What makes teething uncomfortable is that emerging teeth trigger a localized inflammatory response in the gum tissue, releasing the same immune chemicals your body produces during any injury.
What Happens Inside the Gums
Teeth don’t simply slide through the gums. The process involves active remodeling of bone and soft tissue over weeks. While a tooth is still buried in the jawbone, specialized cells dissolve the bone sitting above the developing crown, carving a path upward. At the same time, new bone forms beneath the tooth’s root, pushing it toward the surface. Think of it as a coordinated effort: one crew clearing the road ahead while another crew builds the road behind.
Once the tooth reaches the gum line, the tissue covering it thins, merges with the outer layer of the gum, and eventually breaks open. Before a tooth appears, you can often see a firm, slightly pale bulge on the gum that mirrors the shape of the crown underneath. Occasionally, fluid or a small amount of blood collects in the space above the tooth, creating a bluish-purple bump called an eruption hematoma. This looks alarming but resolves on its own once the tooth cuts through.
The final push from gum line to full height relies on fibers in the tissue surrounding the tooth root. These collagen fibers shorten and tighten as they mature, generating a pulling force that draws the tooth upward into position. Root growth and continued bone formation at the base add to that upward momentum.
Why Teething Hurts
As a tooth pushes through gum tissue, the body treats it like a small wound. The gums release inflammatory signaling molecules, the same ones involved in swelling and pain anywhere in the body. These molecules recruit immune cells to the area and sensitize local nerve endings, which is why the gums become swollen, red, and tender to the touch. The inflammation is real, but it’s localized to the gum tissue directly over the erupting tooth.
This immune response also explains why some babies seem more bothered than others. The intensity of inflammation varies from child to child and even from tooth to tooth in the same child. Molars, which have a broader surface area to push through, tend to cause more discomfort than narrow front teeth.
When Each Tooth Typically Appears
According to the American Dental Association, the lower central incisors (the two bottom front teeth) are usually first, arriving between 6 and 10 months. The upper central incisors follow at 8 to 12 months. From there, the pattern moves outward and backward:
- Lateral incisors (the teeth flanking the front two): 9 to 16 months
- First molars: 13 to 19 months
- Canines (the pointed teeth): 16 to 23 months
- Second molars: 23 to 33 months
These ranges are wide for a reason. A baby who gets a first tooth at 4 months and one who doesn’t get one until 12 months are both within normal variation. Genetics, nutrition, and overall growth rate all influence timing. If your child has no teeth by around 18 months, it’s worth mentioning to a pediatric dentist, but isolated late eruption is rarely a sign of a problem.
Real Symptoms vs. Coincidence
Teething gets blamed for everything from fevers to diarrhea, but the research tells a narrower story. Symptoms that are consistently linked to tooth eruption include sore and swollen gums, drooling, increased biting or chewing, irritability, disrupted sleep, ear rubbing, facial rash (from drool irritating the skin), and decreased appetite for solid foods. In one large review, gum irritation was reported in about 87% of teething episodes, irritability in 68%, and drooling in 56%.
Teething can raise body temperature slightly, but not enough to qualify as a fever. Normal body temperature sits around 98.6°F (37°C), and a true fever starts at 100.4°F (38°C). Multiple studies have found that teething may nudge temperature upward within the normal range but does not push it past the fever threshold. If your baby has a temperature of 100.4°F or higher, something other than teething is responsible.
Symptoms that are not significantly associated with teething include high fever, diarrhea, vomiting, cough, congestion, and rashes on the body (as opposed to the face). The 6 to 30 month teething window overlaps with the period when babies lose passive immunity from their mothers and start encountering common infections for the first time. That timing coincidence is likely why teething has been blamed for illness symptoms for centuries.
The Evolutionary Reason for the Timeline
The timing of tooth eruption is tied to weaning. Across mammals, the full set of baby teeth tends to be complete right around the age when offspring transition to independent feeding. In humans, the complete set of 20 primary teeth typically finishes emerging around 2.3 years, which lines up closely with the natural weaning age of roughly 2.5 to 3 years observed in populations without modern feeding practices.
Interestingly, humans wean earlier relative to tooth emergence than most primates. Orangutans, by contrast, wean late compared to when their teeth come in. This suggests that human infant feeding strategies, likely aided by food preparation and cooking, allowed earlier weaning than teeth alone would support. Still, the basic pattern holds: teeth arrive as a baby’s diet shifts from exclusively liquid to increasingly solid food, providing the chewing surfaces needed to process that food.
Safe Ways to Ease the Discomfort
The simplest and safest approaches work through gentle pressure on the gums. Rubbing a clean finger firmly across the swollen area provides counter-pressure that can temporarily dull the ache. A solid rubber teething ring, chilled in the refrigerator (not the freezer, which can make it hard enough to bruise gums), gives babies something safe to gnaw on.
What you should avoid matters as much as what works. The FDA warns against using topical gels or creams containing numbing agents like benzocaine or lidocaine on infants’ gums. Benzocaine can cause a rare but serious blood condition that reduces the blood’s ability to carry oxygen. Lidocaine solutions can cause seizures, heart problems, and severe brain injury in young children if too much is applied or accidentally swallowed. Homeopathic teething tablets have also drawn FDA warnings. The American Academy of Pediatrics recommends against all of these products for teething pain.
Cold, soft foods like chilled fruit in a mesh feeder can help older babies who have started solids. A clean, damp washcloth that’s been cooled in the fridge also works well as a chewing surface. For babies who are clearly uncomfortable and having trouble sleeping, ask your pediatrician about age-appropriate pain relief options.