4 Season® Ultimate Baby Sleep Bag, Merino Wool & Organic Cotton, Birch Gray

What is a baby sleep bag or sack?

A baby sleep bag, also called a wearable blanket or sleep sack, is a bag-like garment or covering worn by infants for sleeping. It replacing loose blankets in the crib that can cover your baby's face and interfere with breathing.  

Since 2005, The American Academy of Pediatrics has recommended the use of wearable blankets for safe sleep. Unlike regular blankets, a wearable blanket or sleep sack is worn over your child's sleepwear, so it won't be kicked off and baby stays covered all night. The sleep bag will become part of your child's bedtime routine, providing a sense of security and comfort.

 What is the TOG rating of your sleep bags? Are they winter or summer weight?


Our 4 Season baby sleeping bags are designed to be worn year round. They are made from 100% natural breathable fibers and contain NO synthetic filling. Therefore, they do not have a fixed TOG. The fine merino wool lining helps naturally in regulating baby’s body temperature, keeping baby warm in winter and cool in summer.

Woolino sleep bags are recommended to be used in room temperatures 63-75F (17-24C). Simply adjust the layers of sleepwear worn under the sleeping bag to suit the nursery temperature. You can find our suggested dressing guidelines on the back of the room thermometer that comes with every baby sleep bag.

What is the difference between Woolino Ultimate (universal size) and Woolino Basic Baby Sleep Bags?


Both collections have same weight fabrics, merino wool lining and organic cotton outer. The differences are:

Woolino 4 Season Ultimate Baby Sleep Bag has universal sizing: 2m-2yr, underarm snaps for adjusting the size of the armholes, travel slots for use in car seats, strollers, bouncers etc., & both shoulder snaps.

Woolino 4 Season Basic Sleep Bag has simpler design: no snaps and no travel slots; it comes in traditional sizes: 0-6, 6-18, 18-36 months.

Woolino sleep bags sizing chart?

We do not recommend sizing up. The sleep bag should be well-fitted around your child's upper body for a safe and secure fit. We suggest using our recommended sizing guidelines to find the correct size based on your child's age, height, and weight.

When can my baby start using Woolino Ultimate Baby Sleep Bags in size 2m-2yr? How long will my baby fit in this Woolino sleeping bag?

Woolino Ultimate Baby Sleep Bags provide an excellent value as they are designed to fit an average size baby from about 2 months up to 2 years of age. You may start using your sleeping bag when you feel your baby is too big to be swaddled and is breaking out of it. Please use the under-arms snaps to adjust the fit for smaller babies. Our minimum recommended weight is 10lb. or 4.5 kg.

When should I use the under-arm adjustment system?

In general, you need to use the under-arm snaps for babies up to 6 months old. However, this depends on baby’s size, so for smaller babies you may have to use them longer. Please keep in mind that the underarm snaps are to be used for safety reasons, so that the sleep bag fits snugly around baby’s upper body and doesn’t climb up baby’s face.

Do I need more than one Woolino sleeping bag?

Yes, we recommend having two Woolino baby sleeping bags. It is always useful to have a spare sleep bag when one is being washed, to keep at grandparents' place or if baby requires a quick change in the middle of the night. Please enter code BOGO20 at checkout to receive our buy one item, get one item 20% off promotion. This promotion cannot be combined with any other offer.

Won’t wool itch my baby’s skin?

Absolutely not. We use only superfine merino wool, which unlike the traditional wool, feels like silk against baby’s delicate skin. In fact, because of its softness and unique breathability, it is perfect for helping treating conditions such as heat rash and eczema.

Isn’t merino wool too hot for warm temperatures/climates?

Our merino wool baby sleeping bags are perfect for year-round wear in nurseries with room temperatures 63-75F (17-24C). Simply adjust the layers of underwear or sleepwear worn beneath the sack to suit the room temperature. Merino creates a micro-climate around your baby’s body, gaining or losing heat as required to produce warmth in cool conditions and enhance cooling effects in warm conditions.

What should my baby wear when sleeping in a Woolino 4 Season Sleep Bag?

We recommend sleepwear made of natural and breathable fabrics like cotton or merino wool. Please refer to the dressing guide we provide (also on back of your Woolino room thermometer) as general recommendations on how to dress your baby depending on the room temperature. Woolino pajamas are ideal for layering or to wear inside a Woolino sleep bag. The temperature in most rooms will rise and fall throughout the night, and the merino fiber has the remarkable ability to regulate your baby's body temperature.

How do I know if my child is hot or cold?

Please check if your baby is hot or cold while sleeping by touching her tummy or behind her neck. Touching baby’s hands and feet are not good indications of their actual body temperature.

Why don’t the sleeping bags have sleeves? Won’t my child get cold?

Our baby sleeping bags are sleeveless to ensure air circulation around baby’s chest. Babies that sleep with traditional sheets and blankets rarely sleep with their arms underneath the blankets. We recommend layering under-garments to ensure your child is perfectly comfortable in their sleeping environment. It is normal for babies to have cold hands and feet due to their still-developing circulation systems and it is not an indication that they are cold. Checking behind baby’s neck or his/her tummy will give you better indication of baby’s body temperature.

Does the sleep bag need to be washed before the first use?

It is not required to wash your Woolino sleep bag before wearing. When you wash it, please follow the care instructions carefully.

Why does wool smell when it gets wet?

There is an odor associated with wet wool, sometimes described as a "wet dog", "burned", or "perm" smell. This particular smell of wet wool is present because we use natural merino wool that has been minimally processed in order to preserve the lanolin content inside the wool.

Lanolin is naturally present in merino wool and is responsible for giving wool all of the great properties that we love: wicks away sweat, resists stains, feels soft to the touch, stays elastic, and resists bacteria and odors. Wool is a natural product. Even if you have multiple products, one may have a higher lanolin content than the other, accounting for a difference in smell.

You should not notice this smell at all when the product is completely dry. Over time, the smell will be less and less noticeable after washing as the lanolin content in the wool dissipates.

How should I care for my Woolino sleep bag?

Merino wool by nature is self-cleaning and does not need to be washed as frequently as other fabrics. To refresh and reduce washing, air the garment often.

• Machine wash: Close zipper. Wash on Low, 85°F /30°C max
• Use wool or mild detergent.
• Line-dry clothing and blankets. Sleep bags can be tumble dried on No Heat or Air Dry settings.

How to remove stains from wool?

Stains should be treated immediately. Do not apply any form of heat, as this tends to fix most stains making them more difficult to remove. 
Rinse the stain immediately and thoroughly in cold water. Then, apply one of these two homemade stain remover mixtures that we recommend: