Lisp in Children: Types, Causes, and When to Worry
A lisp is a specific error on the S and Z sounds, usually because the tongue is in the wrong place. A mild frontal lisp — where S sounds like “th” (“thun” for “sun”) — can be a normal part of development up to about age 4½. A lisp that persists past then, or a wet-sounding “lateral” lisp at any age, is worth having a speech-language pathologist assess.
What is a lisp?
A lisp is a specific speech-sound error that affects the “s” and “z” sounds. Instead of a crisp, hissing S, the sound comes out distorted — most often like a “th,” or with a wet, slushy quality. Because it is limited to a couple of sounds, a child with a lisp is usually easy to understand in most words.1
A lisp is a type of articulation error — the sound is being formed in the wrong place. That is different from a broader phonological pattern that affects whole groups of sounds. Knowing which one you are dealing with shapes how it is treated.1,2
The four types of lisp
Speech-language pathologists describe four lisp types. The difference is where the tongue goes and where the air escapes — and it matters, because two of them are common and developmental while the other two are not.1
| Type | What happens | What it sounds like | Typical outlook |
|---|---|---|---|
| Frontal (interdental) | Tongue slips between the front teeth | “th” for S — “thun” for “sun” | Common; can be normal to ~age 4½ |
| Lateral | Air escapes over the sides of the tongue | Wet, “slushy” S | Not typical — worth an evaluation |
| Dentalized | Tongue pushes flat against the back of the front teeth | Muffled, dull S | Often developmental; watch if it persists |
| Palatal | Tongue lifts toward the roof of the mouth | Distorted, “h”-tinged S | Not typical — worth an evaluation |
The four lisp types.
Lateral and palatal are the ones to watch
Frontal and dentalized lisps often show up in normal development. A wet lateral lisp or a palatal lisp does not — if you hear either, it is worth having a speech-language pathologist take a look, at any age.
Is a lisp normal at my child’s age?
A mild frontal lisp can be a normal part of speech development while the S and Z sounds are still coming in. Most children produce a clear /s/ by about age 4 to 5, so a “th”-like S in a 3- or 4-year-old is often just part of that process.11,5
- Under ~4½: a mild frontal lisp is often developmental and may resolve on its own.
- Past ~4½–5: a lingering frontal lisp is worth assessing, since it is less likely to fade and easier to fix earlier.
- Any age: a wet, slushy lateral lisp (or a palatal lisp) is not part of typical development and warrants an evaluation.
What causes a lisp
Most lisps come down to tongue placement — the tongue simply learned a slightly-off position for S. In many children there is no deeper cause; it is a habit that formed as speech developed.1
Sometimes a lisp is linked to other factors a speech-language pathologist will consider: a tongue-thrust swallowing pattern that pushes the tongue forward, the spacing or alignment of the teeth, or a long-standing thumb-sucking or pacifier habit. These do not always cause a lisp, but they can make one more likely to stick.3
How a lisp is assessed and treated
A speech-language pathologist listens to S and Z in different words and positions, identifies the lisp type, and checks whether anything else — like a phonological pattern — is going on. From there, therapy teaches the tongue a new, correct position for S.1,9
The core of treatment is practicing the correct S in real words — starting simple and building up — often with a mirror and clear cues (“keep your tongue behind your teeth,” “make a long snake sound”). Non-speech mouth exercises are not needed; practicing the sound itself is what works.1
Free Lisp Assessment
Check whether your child’s S sounds like a lisp — and which type.
When to see a speech-language pathologist
When to get an evaluation
See an SLP if a lisp persists past about age 4½ to 5, if you hear a wet “slushy” lateral lisp (or a palatal lisp) at any age, if your child is hard to understand, or if home practice is not helping.
A certified speech-language pathologist can identify the lisp type and target it directly — in person or by teletherapy, which is effective for many children. Earlier is generally easier, since a newer habit is quicker to reshape than one that has set in over years.8,7
You often do not need to wait for a referral. Your local school district can evaluate a child age 3 and older, and you can also find a certified SLP privately through ASHA’s directory.10,3
Frequently asked questions
Is a lisp normal in young children?＋
A mild frontal lisp — where the tongue slips between the teeth so S sounds like “th” (“thun” for “sun”) — can be a normal part of development up to about age 4 to 4½ while the S and Z sounds mature. A lisp that persists past about age 4½ to 5, or a wet-sounding lateral lisp at any age, is not part of typical development and is worth assessing.
What are the types of lisp?＋
There are four: a frontal (interdental) lisp pushes the tongue between the teeth so S sounds like TH; a lateral lisp lets air spill over the sides of the tongue for a wet, “slushy” sound; a dentalized lisp pushes the tongue flat against the back of the front teeth; and a palatal lisp lifts the tongue toward the roof of the mouth. Frontal lisps are common and often developmental; lateral and palatal lisps are not typical and usually warrant an evaluation.
Does my child have a lisp?＋
A lisp shows up specifically on S and Z. Listen for “th” in place of S (“thnake” for “snake”), or a wet, slushy quality to S. If those sounds are distorted while the rest of speech is clear, a lisp is likely. A quick screening — or SpeechStep’s free lisp assessment — can help you tell the type and whether it is worth a professional look.
Will my child outgrow a lisp?＋
Many mild frontal lisps resolve on their own as S develops, often by age 4½ to 5. Lateral and palatal lisps rarely resolve without help. Because early therapy is quicker and easier than correcting a habit years later, it is worth getting a lisp checked if it persists or sounds slushy, rather than simply waiting.
What causes a lisp?＋
Most lisps are simply a matter of tongue placement — the tongue learns a slightly-off position for S. Occasionally a lisp is linked to things like a tongue-thrust swallowing pattern, dental spacing, or a long thumb-sucking habit. A speech-language pathologist can tell whether the cause is placement alone or something worth addressing alongside it.
When should I see a speech therapist about a lisp?＋
See a speech-language pathologist if a lisp persists past about age 4½ to 5, if you hear a wet or slushy lateral lisp at any age, if your child is hard for others to understand, or if home practice is not helping. An SLP can identify the lisp type and target it directly, in person or by teletherapy.
Put this into practice today
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References
11 sources from authoritative bodies. Last reviewed July 2026.
- 1.ASHASpeech Sound Disorders: Articulation and Phonology — Practice Portal page.
- 2.ASHASelected Phonological Patterns — Practice Portal page.
- 3.ASHASpeech Sound Disorders — Consumer page.
- 4.ASHATypical Speech and Language Development — Consumer page.
- 5.ASHACommunication Milestones: 4 to 5 Years — Developmental milestones.
- 6.ASHACommunication Milestones: Age Ranges (Birth to 5) — Developmental milestones.
- 7.NIDCDSpeech and Language Developmental Milestones — Fact sheet.
- 8.ASHATelepractice — Practice Portal page.
- 9.ASHAScope of Practice in Speech-Language Pathology — Policy document.
- 10.ASHAASHA ProFind — Find a Certified SLP — Clinician directory.
- 11.Peer-reviewedCrowe & McLeod — Children’s English Consonant Acquisition in the United States: A Review — Systematic review (AJSLP), 2020.