If your child says "thun" for "sun" or their "s" sounds slushy and unclear, you may be wondering whether it is just a cute stage or something that needs attention. A lisp is one of the most common speech sound differences in young children, and the right response depends a great deal on which type of lisp it is and how old your child is. This guide explains the different types of lisp, which ones children usually grow out of, and when it is worth talking to a speech and language therapist.
Key takeaways
A lisp is a difficulty producing the "s" and "z" sounds, and sometimes "sh", "ch" and "j" sounds too.
An interdental lisp, where the tongue pokes between the teeth so "s" sounds like "th", is common in young children and many grow out of it by around age four and a half to five.
A lateral lisp, where air escapes over the sides of the tongue and speech sounds "slushy" or wet, is not part of typical development at any age and usually needs therapy to resolve.
Lisps are rarely caused by anything a parent did or did not do. Tongue placement habits, dental changes and individual development all play a part.
Speech and language therapy for a lisp is well established, practical and often enjoyable for children, and it works well online.
In Ireland you can access help through HSE primary care services or privately through a CORU-registered speech and language therapist, with no referral needed for private care.
What exactly is a lisp?
A lisp is a type of speech sound difficulty, known clinically as an articulation disorder, that affects the sibilant sounds. Sibilants are the hissy sounds of speech: "s" and "z" most of all, and sometimes "sh", "ch" and the "j" sound in "jam". To make a clear "s", the tongue tip needs to sit just behind the top front teeth, without touching them, while a fine jet of air flows down the centre of the tongue. It is a surprisingly precise movement, which is why it is one of the later skills to settle in a child's speech development.
When the tongue sits in the wrong place, or the air flows over the wrong part of the tongue, the sound comes out distorted. That distortion is what we hear as a lisp. Some lisps are simply an immature pattern that fades with time. Others are a habit that has become established and is unlikely to change without help.
The four types of lisp
Speech and language therapists generally describe four types of lisp. Knowing which one your child has is the single most useful piece of information, because it largely determines whether to wait or to act.
Interdental lisp: The tongue tip pokes out between the front teeth, so "s" and "z" sound like "th". "Sun" becomes "thun" and "zoo" becomes "thoo". This is the classic lisp most people picture, and it is very common in toddlers and preschoolers. Many children grow out of it as their speech matures.
Dentalised lisp: The tongue pushes against the back of the front teeth rather than poking through them. The result is a muffled, slightly dull "s". Like the interdental lisp, this is often seen in younger children and frequently resolves on its own.
Lateral lisp: Instead of flowing down the centre of the tongue, air escapes over one or both sides. The result is a wet, slushy quality to "s", "z" and often "sh" and "ch" as well. Some people describe it as sounding like the child has too much saliva in their mouth. This is the important one for parents to know about: a lateral lisp is not a normal stage of speech development at any age, and children very rarely grow out of it without therapy.
Palatal lisp: The middle of the tongue rises up and touches the soft palate while the child attempts the sound, producing an unusual distortion. Like the lateral lisp, this is not developmental and generally needs direct therapy.
If you are unsure which type your child has, a short assessment with a speech and language therapist will identify it quickly. As a rough home check, listen for the difference between a clean "th"-like substitution, which suggests an interdental lisp, and a slushy or spitty quality, which suggests a lateral lisp.
Is a lisp normal at my child's age?
Context matters enormously here, so it helps to think in age bands.
Toddlers and young preschoolers (2 to 4 years): An interdental or dentalised lisp in this age group is common and usually nothing to worry about on its own. Children's speech sound systems are still developing, and "s" is a late-settling sound. At this age, focus on the bigger picture: is your child understood by familiar adults most of the time, and is their language developing well?
Around 4 and a half to 5 years: This is the point where many therapists suggest taking a closer look at a persisting interdental lisp. School entry is approaching, other children become more aware of speech differences, and research on speech sound development suggests that distortions still present at this stage are less likely to fade on their own.
School age and beyond: An interdental lisp that persists into the school years usually will not correct itself, though it remains very treatable. Older children often make quick progress because they can understand what they are working on and hear the difference in their own speech.
Any age: A lateral or palatal lisp is worth assessing whenever you notice it. Because these patterns are not part of typical development, waiting rarely helps, and an established habit takes longer to change than a newer one.
One more consideration outweighs all the age guidance: your child's own feelings. If a child of any age is being teased, avoiding speaking, or becoming self-conscious about their speech, that alone is a good reason to seek support.
What causes a lisp?
Parents often worry that they caused a lisp somehow, or missed something they should have caught. In almost all cases, that is not true. Common contributing factors include:
Tongue placement habits: The most common cause is simply a motor habit. The child learned the sound with the tongue in a slightly wrong position, and the pattern stuck.
Dental and jaw changes: Losing baby teeth, the position of the front teeth and the way the jaw grows can all influence sibilant sounds, sometimes temporarily.
Prolonged soother or thumb habits: Long-term dummy or thumb sucking may encourage a forward tongue posture in some children, though it is one factor among many rather than a simple cause.
Hearing: Frequent ear infections or glue ear can muffle the high-frequency hiss of "s" sounds during the years a child is learning them. If your child has a history of ear trouble, mention it at assessment.
Oral structure: Occasionally, features such as a significant tongue-tie or an open bite play a role. A therapist will consider this during assessment and refer on to dental or medical colleagues if needed.
What does not cause a lisp: bilingualism, laziness, or copying a sibling. These are common worries and none of them holds up.
When and how to get help in Ireland
If you decide it is time for an assessment, you have two main routes.
HSE primary care speech and language therapy is free, and you can refer your child yourself without going through a GP. The honest reality, as many Irish parents know, is that waiting times for assessment and then for therapy vary widely between areas and can be long. If you are concerned, it is still worth getting on the list early, because you can always come off it if the lisp resolves.
Private speech and language therapy offers faster access, typically within days or weeks. In Ireland, always check that a private therapist is CORU registered, which is the legal requirement for anyone practising under the title of speech and language therapist. The Irish Association of Speech and Language Therapists (IASLT) is the professional body and a useful source of information. Private fees can often be claimed against tax as a health expense, and some health insurance plans contribute too.
Online therapy works particularly well for lisps. Sibilant sounds are high-frequency and transmit clearly over good audio, the therapist can model tongue placement close to the camera, and school-age children, who make up most lisp caseloads, engage well with screen-based practice. It also means access to a therapist does not depend on where in Ireland you live.
What speech therapy for a lisp looks like
Therapy for a lisp is structured, practical and usually enjoyable. A typical journey looks like this:
Assessment: The therapist listens to your child's speech in single words, sentences and conversation, looks at oral movements, and identifies the type of lisp and whether any other sounds are affected.
Establishing the new sound: The therapist teaches the correct tongue position, often using visual cues, mirrors, and playful analogies like keeping the "snake sound" behind the "teeth fence". For lateral lisps, therapists often build a clear "s" from a long "t" sound, which naturally directs air down the middle of the tongue.
Practising in bigger chunks: Once your child can produce a clear "s" on its own, therapy moves through syllables, words, phrases and sentences, gradually increasing the challenge.
Carryover into everyday talking: The final and often longest stage is helping the new sound become automatic in conversation, at school and at home. Home practice makes the biggest difference here.
Most children with a straightforward lisp do not need years of therapy. Regular short sessions with consistent home practice between them is the usual pattern, and progress is very visible, which children find motivating.
What you can do at home
Whether you are waiting for an assessment or supporting therapy that is already underway, home habits matter.
Model, do not correct: If your child says "thock", respond naturally with the correct model: "Yes, your sock!" Avoid asking them to repeat words correctly unless a therapist has shown you how, because drilling a sound the wrong way can strengthen the wrong habit.
Keep the focus on the message: Respond to what your child says, not how they say it. Confidence in communicating is worth protecting.
Do the therapy homework little and often: Five minutes a day beats one long session a week. Attach practice to a routine, such as after dinner or in the car.
Watch the teasing: If siblings or classmates imitate or mock the lisp, take it seriously and shut it down kindly. Self-consciousness can make children talk less.
Address soother habits gently: If your child still uses a dummy beyond toddlerhood, work towards phasing it out, ideally keeping it to sleep times first.
Get hearing checked if in doubt: If there is any history of glue ear or frequent infections, ask your GP or public health nurse about a hearing test.
The bottom line
A lisp in a young child is common, and an interdental lisp often fades on its own before school age. The two situations that deserve a professional ear are an interdental lisp that persists past around four and a half to five years, and a slushy lateral or palatal lisp at any age, because those patterns rarely resolve without help. Therapy for lisps is well established and effective, children generally enjoy it, and it works well online. If you are unsure which type of lisp your child has, a single assessment will tell you where you stand, and if your child is happy and easily understood, you have time to make decisions calmly.
References
Related on Lingo
Online speech and language therapy in Ireland, with no referral or waiting list.
This article is based on current peer-reviewed research and clinical guidelines. It is intended for informational purposes and does not replace professional clinical advice.