Let’s talk about thumb sucking. Or finger sucking. Or hand chewing. Or that intense relationship with the cuddly that ends up slobbered on by morning. Whatever it looks like—it's all the same soothing instinct at play. And for many parents, it's a bit of a love-hate relationship. On one hand (pun intended), it's adorable and clearly comforting. On the other, you might be worrying about teeth, habits, or whether it’s "okay" in the long run.

So, let’s break it down.

Thumb sucking, finger sucking, cuddly sucking, hand sucking – it's all sucking to soothe.

Babies are born with the sucking reflex—it’s literally a survival mechanism. They suck to feed, and they also suck to calm. If you’ve ever watched a scan of a baby in utero with their thumb in their mouth, you’ll know this starts well before they even make their grand entrance earthside.

So yes, whether it’s a thumb, finger, fist, or corner of a beloved blankie, sucking = soothing. It’s their version of a weighted blanket, a deep breath, or a favourite Spotify playlist on a rough day.

Why thumb sucking is self-soothing.

Self-soothing is the holy grail of baby sleep, right? We talk about it a lot in the sleep world, it’s something all babies have to learn to do eventually. The good news is, if you have a thumb or finger sucker you will likely have an early self-soother. They are attached to their soothing mechanism.

Thumb sucking is one of the earliest and easiest forms of self-soothing. It’s always available (unless they’re swaddled—more on that soon), it doesn’t fall out like a dummy, and babies can control it themselves (after a few months). When they find that magical little digit and give it a good suck, it releases dopamine and serotonin, the feel-good chemicals that help them regulate their emotions and drift into slumber.

Thumb suckers = great sleepers.

Now, I’m not saying every thumb-sucking baby sleeps through the night. But in my experience as a sleep consultant here in NZ, babies who find their thumbs tend to be much more capable of settling themselves to sleep and linking sleep cycles.

Why? Because their soothing mechanism is literally at their fingertips.

They don’t need Mum or Dad to pop a dummy back in, pat their bum, or rock them for 30 minutes. They wake, they suck, they settle. Magic.

Why thumb sucking helps with longer naps and nights.

One of the biggest challenges for babies between 4–6 months is connecting sleep cycles—especially for naps. The ability to resettle between those 45-minute cycles often hinges on whether they have a reliable way to soothe themselves.

Thumb sucking can be the golden ticket. It gives them a consistent, calming tool to help bridge those cycles. That’s when you start seeing those beautiful 1.5–2 hour naps and long overnight stretches.

But what about the teeth? (The cons)

Ah, yes. The dental side. This is where things get a little trickier.

Long-term thumb or finger sucking can cause dental issues—especially if it continues past the age of 4–5 when adult teeth start coming through. Things like an open bite or changes in the palate shape can happen if the habit sticks around too long or is particularly forceful.

But here’s the thing: not every thumb sucker ends up with orthodontic issues. The key is monitoring the intensity and duration of the habit and intervening if it's still going strong as they head into preschool years.

How (and when) to quit thumb sucking.

I’m often asked, “Should we stop it now?” And honestly, if your baby is under 2 and it’s helping with sleep, I say ride the wave. Most kids wean themselves naturally as they grow and discover other ways to self-regulate.

But if you're looking to phase it out—especially if it's affecting teeth or becoming a habit in older toddlers—thumb guards can be helpful. There are gentle ones that simply make sucking less satisfying, which encourages kids to stop on their own. The key is doing it with compassion and patience, never shame.

Start the conversation with your child (if they’re old enough), and make a plan together. A reward chart, a bedtime story about quitting thumb sucking, and a consistent approach go a long way.

Most dentists also sell thumb or finger guards which look like a little plastic brace, this attaches to the hand and velcro’s in place. It very quickly deters your little one from thumb or finger sucking and can’t be worn away unlike the foul-tasting nail polish of the past.

Case Study: The 5-Month-Old Who Found Her Thumb and Found Her Sleep

Let me tell you about one little girl I worked with recently. At 5 months old, she was waking every 45 minutes overnight and barely napping. She was swaddled tightly—like most babies at that age—and couldn’t access her hands.

We suggested to Mum that it was time to transition out of the swaddle. A bit nerve-wracking, yes, but worth it. Mum was nervous as when the baby was younger she had observed her sucking her thumb, and then the hand would fly out and the baby would cry. This was initially why mum swaddled the baby, the thumb sucking wasn’t working.

I explained that baby likely has a lot more motor control at this age, and will in all likelihood be able to keep their thumb in at this age.

Night one out of the swaddle? Baby found her thumb. Night two? She only woke once. By the end of the week, she was napping for over an hour at a time and sleeping 6 hours, having a feed and going back to sleep for a further 5 hours. Night two was just as successful with the first stretch of sleep pushing to 8 hours.

Sometimes the answer isn’t more intervention—it’s giving babies the chance to use the tools they already have.