Parent question

Lateral lisp: when S sounds slushy

Published 21 October 2026 · Updated 21 October 2026

The short answer

In a lateral lisp, air escapes over the sides of the tongue instead of down the middle, so S and Z sound slushy or wet. Unlike a “th” lisp, which is common in young children, a lateral lisp isn’t part of typical development, so it’s worth asking a speech-language pathologist (SLP) about it rather than waiting for it to fade. It can affect SH, CH and J too.

What’s happening

For a clear S, the tongue makes a groove down the middle with its sides raised, so air flows out at the front. In a lateral lisp, the sides of the tongue are down and air comes out over one or both sides (Preston, Leece & Maas, 2016; Bode et al., 2023).

Frontal and lateral lisps compared
	Frontal (“th”) lisp	Lateral lisp
What you hear	“thun” for sun	A slushy, wet S
Where the air goes	Out the front, with the tongue between the teeth	Over the sides of the tongue
Typical development?	Common in young children	Not part of typical development

Is it normal?

A UK NHS speech therapy service describes a frontal lisp as typical until about age 5, but says a lateral lisp isn’t part of typical development (Whittington Health NHS Trust).
In an Australian community study of 4 to 5-year-olds assessed after a parent or teacher raised a concern, 13.3% had lateral lisps (McLeod et al., 2013). That isn’t a rate for all children, but it shows they aren’t rare.
It can last. One published case was an 11-year-old who still had a lateral S (McAuliffe & Cornwell, 2008).

Which sounds it affects

Lateral lisps are best known on S and Z, but the same pattern can affect other hissing and hushing sounds. Studies of children with these errors found lateral sounds on SH and CH as well as S (Gibbon, Hardcastle & Dent, 1995; Preston, Leece & Maas, 2016). J, which is made like CH with the voice on, can be affected too. See the SH, CH and Z guides.

Tongue-tie, teeth and bite

Tongue-tie. A systematic review found no clear link between tongue-tie and speech errors (Wang et al., 2022). See tongue-tie and speech.
Bite. An open bite, where the front teeth don’t meet, is the bite difference most often linked to speech sound errors, though mainly to frontal lisps (Bode et al., 2023).
An SLP will check the mouth as part of an evaluation and can suggest a dentist or orthodontist if needed (ASHA).

How therapy helps

Learning the new position. An SLP teaches where the tongue goes, and may use touch cues, like a tongue depressor, to help a child feel the right spot (ASHA).
Seeing the tongue. Some clinics use technology that shows tongue position: electropalatography (a thin palate sensor) or ultrasound. An 11-year-old improved after 12 electropalatography sessions and a 6-week home program, and ultrasound has been used in small studies that included children with lateral sounds (McAuliffe & Cornwell, 2008; Cleland et al., 2019). These are small studies, and most children are treated without special equipment.
Building it up. Once the new S is there, practice moves from syllables to words, sentences and conversation. See the articulation hierarchy.

Questions parents ask

Will a lateral lisp go away on its own?

A lateral lisp isn’t part of typical development, so don’t count on it fading without help. Ask an SLP whenever you notice it.

What’s the difference between a lateral lisp and a frontal lisp?

In a frontal lisp, the tongue pushes between the teeth and S sounds like “th”, which is common in young children. In a lateral lisp, air escapes over the sides of the tongue and S sounds slushy.

Can a lateral lisp be fixed in older children?

Therapy can still help older children. One published case report describes an 11-year-old whose lateral S improved after intensive therapy and a home program.