Reviewed by a licensed speech-language pathologist
Quick answer: A frontal lisp pushes the tongue forward so an s sounds like th, and it is common and often temporary in young children. A lateral lisp lets air spill over the sides of the tongue for a slushy sound, and it is not a typical stage. Knowing which one a child has shapes what to do next.
Plenty of small children say “thun” for “sun” and it charms everyone at the dinner table. But not all lisps are the same, and some are easier to shrug off than others. The word lisp actually covers a few different patterns, and telling them apart helps a parent judge whether a child is likely to grow out of it or would benefit from a closer look. Among the types of lisp, the two that come up most often are the frontal lisp and the lateral lisp.
What is a lisp, exactly?
A lisp is a specific kind of speech sound difference that affects the s and z sounds, and sometimes the related “sh” and “ch” family. These sounds depend on a precise stream of air passing over the tongue and out the front of the mouth. When the tongue sits in the wrong spot, or the air escapes the wrong way, the sound changes. The American Speech-Language-Hearing Association groups lisps within the broader area of speech sound disorders, which describe how children make and combine the sounds of speech.
It helps to remember that s and z are late-developing sounds. Research summarized by ASHA on developmental norms shows many children are still refining these sounds well into the early school years, so a young child who lisps is not automatically behind.
How does a frontal lisp sound and look?
A frontal lisp, sometimes called an interdental lisp, happens when the tongue pushes forward against or between the front teeth during s and z. The result is a sound close to the “th” in “thin.” So “soup” comes out as “thoup” and “zoo” as “thoo.”
This is the pattern most people picture when they hear the word lisp. It is common in preschool and early childhood, and it frequently overlaps with the natural stage of losing baby teeth, since a gap in the front teeth gives the tongue an easy place to slip through. For many children a frontal lisp fades as the mouth matures and the adult teeth come in.
How does a lateral lisp sound and look?
A lateral lisp is different in both cause and sound. Instead of coming forward, the tongue blocks the center airflow, so air leaks out over the sides. This produces a wet, slushy, or “spraying” quality that some people describe as a “slushy s.” Words like “sun” can sound muffled and airy at the edges.
The key difference for parents is that a lateral lisp is not a normal part of typical sound development. It does not usually appear and then disappear the way a frontal lisp can. Because of that, a lateral lisp at any age is a reasonable reason to seek an evaluation rather than to wait.
When is a lisp just a phase, and when is it a concern?
Timing matters. Many children produce clean s and z sounds by around age seven or eight, and a frontal lisp before that range is often within the expected spread. HealthyChildren.org from the American Academy of Pediatrics and the CDC’s milestone guidance both give parents age-based checkpoints for speech, and these are useful for spotting a gap that is widening rather than closing.
A few signals suggest it is worth acting sooner rather than later: any lateral lisp, a frontal lisp that is still strong past age seven, a child who is frustrated or hard to understand, or a lisp paired with other speech or language concerns. When in doubt, an assessment costs little and answers a lot.
How is a lisp evaluated and treated?
A speech-language pathologist listens to how a child produces sounds in different words and positions, watches tongue placement, and checks hearing and oral structure when relevant. If therapy is recommended, it usually centers on teaching the tongue where to sit and how to direct the airstream, first in single sounds and then in longer words and sentences.
Between sessions, short and playful practice at home tends to speed progress, because a new tongue placement needs many light repetitions to become automatic. Some families lean on a speech-sound practice companion such as Little Words to give a child voice-first, low-pressure practice through play during the week. That kind of daily home practice works best as a supplement to a therapist’s plan, not a replacement for it, and it should stay short and cheerful rather than becoming a chore. Mayo Clinic notes that many articulation differences respond well to targeted speech therapy, especially when practice is consistent.
What can parents do at home right now?
Model the correct sound clearly without turning it into a lecture. If a child says “thun,” you can simply reply, “Yes, the sun is bright,” giving a clean version rather than asking them to repeat after you. Keep the mood positive, since pressure and correction can make a child self-conscious and quieter. Read together, play sound games, and note which sounds are tricky so you can share specifics with a clinician if you do book an evaluation.
Key takeaways
- A frontal lisp pushes the tongue forward so s sounds like th, and it is common and often temporary in young children.
- A lateral lisp produces a slushy, air-over-the-sides sound and is not a typical developmental stage.
- The s and z sounds develop late, so many children refine them into the early school years.
- Any lateral lisp, or a frontal lisp lingering past age seven or eight, is a good reason to seek an evaluation.
- Targeted therapy plus short, playful home practice usually helps a lisp improve.
Frequently asked questions
What is the difference between a frontal and a lateral lisp?
A frontal lisp pushes the tongue forward so an s sounds like th. A lateral lisp lets air escape over the sides of the tongue for a wet, slushy sound. The frontal type is common in young children; the lateral type is not part of typical development.
Is a lisp normal for a young child?
A frontal lisp is common in preschoolers and often resolves on its own. A lateral lisp is not a normal stage and is more likely to need help from a speech-language pathologist.
At what age should a lisp be gone?
Many children produce clean s and z sounds by around age seven or eight. A frontal lisp lasting past that, or any lateral lisp at any age, is worth an evaluation.
Can a lisp go away without therapy?
A mild frontal lisp in a young child often fades on its own. A lateral lisp rarely corrects itself and usually improves fastest with guided practice.
Does a lisp affect learning or reading?
A lisp is a way of producing sounds and does not lower intelligence. It can affect how easily others understand a child, so addressing it early supports clear communication and confidence.
Sources
- American Speech-Language-Hearing Association: Speech Sound Disorders / Articulation (asha.org)
- ASHA: Developmental Norms for Speech Sounds (McLeod and Crowe, 2018) (pubs.asha.org)
- American Academy of Pediatrics (HealthyChildren.org): Speech Development Milestones (healthychildren.org)
- Centers for Disease Control and Prevention: Developmental Milestones (cdc.gov)
- Mayo Clinic: Speech Sound and Articulation (mayoclinic.org)
