Understanding the Dew Point, Humectants, and Humidity for Curly Hair

January 31, 2019


Verna Meachum

Curly hair frizzing up when the dew point isn't right

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I'm just a girl who transformed her severely damaged hair into healthy hair. I adore the simplicity of a simple hair care routine, the richness of diverse textures, and the joy of sharing my journey from the comfort of my space.

My mission? To empower others with the tools to restore, and maintain healthy hair, and celebrate the hair they were born with!

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As the spring and summer months approach, many of us curlies are concerned with one thing: frizz.

Weather plays a big role in how our hair behaves. What a lot of us may not know is that humidity has little to do with how our hair acts and responds to the climate.

In order for our hair to behave at its best (at least for a lot of us), we must understand the dew point.

In this blog post, we’ll explain what the dew point is, how humectants work, and how humidity affects curly hair.

We’ll also share some tips for keeping your curls looking their best in any weather!

Dew Point, Humectant, and Humidity: How They Influence Curly Hair

Weather and climate conditions have a big impact on hair. Consumers frequently voice concerns about being unable to style and maintain their hairstyle during changing weather conditions.

This is especially obvious during extreme conditions such as a dry, chilly winter or a wet, humid summer.

For example, many curlies find that their hair is drier in the winter months and more prone to frizz in the summertime.

According to hair scientists, hair protein absorbs moisture from the air and this water uptake varies with changing humidity levels.

With higher moisture levels, hydrogen bonds inside hair structures are broken and later reformed. This entire process significantly modifies the hair’s properties.

Curly hair is a special case, in that, it has unique structural characteristics that are more vulnerable to these weather changes.

Furthermore, even within a single day, the weather may alter drastically. This makes it all the more difficult to maintain the desired style.

So, the water content in the air or “air moisture level” is hugely important for hair experts, stylists, and consumers to understand and take into account.

The objective is to preserve the structural integrity of hair to keep its natural appearance.

The “Dew Point,” “Humidity” and “Humectants” are three terms that are frequently mentioned when it comes to hair and weather.

We’ll begin by looking at how weather conditions affect curly hair, and how these three elements play a vital role in the whole discussion.

Let’s first examine some basics…

Dew Point

Dew points can be a deciding factor in figuring out when to use humectants and when to avoid them.

Water molecules are constantly on the move. Evaporation and condensation are taking place simultaneously.

Evaporation is the conversion of liquid water into a gas (steam) while condensation is the other way around, converting steam into liquid water.

Water in the air keeps a balance between the two states depending upon the temperature.

Dew point is the temperature at which water molecules start condensing and small droplets (dew) form.

In other words, the dew point is the temperature where the rate of evaporation is equal to the rate of condensation.

Dew point levels

It would be ideal if there were an app to help us determine which ingredients to use based on the weather conditions!

The next best thing is to understand the dew point levels.

Again, you’ll need to go through some trial and error with your own hair to discover what works best for you, in terms of weather conditions and product combinations.

As always, let your hair be your guide!

Below are some general guidelines for the dew point levels and their relation to when humectants are helpful.

The different dew point levels to check for curly hair


Humidity is the concentration of water molecules present in gaseous form in the air.

The number of water molecules is measured relative to the control situation and is referred to as relative humidity.

The higher the number of water molecules in the air, the higher the humidity level.

Dew point and relative humidity are closely related but dew point is a more accurate way of measuring the moisture in the air.

While dew point is a temperature, relative humidity is represented as a percentage.

Many times, relative humidity can be misleading. For example, a temperature of 30 and a dew point of 30 will give you a relative humidity of 100%, but a temperature of 80 and a dew point of 60 produces a relative humidity of 50%. It would feel much more “humid” on the 80 degree day with 50% relative humidity than on the 30 degree day with a 100% relative humidity. This is because of the higher dew point.

According to the National Weather Service

The higher the dew point rises, the greater the amount of moisture in the air.

How Does the Dew Point and Humidity Impact Curly Hair?

Hair being a biopolymer can absorb water from the surroundings. It may gain 30% weight of its original weight.

Water uptake follows a dynamic balance system where adsorption or desorption varies according to the humidity conditions.

It is a “Two Way Traffic” in which hair absorbs or may desorb (lose) water depending upon the surrounding humidity and dew point. 

As hair absorbs water, it swells and its diameter increases due to the high water level inside. This is even more prominent under high humidity conditions when there is more water outside.

As a result, hair becomes frizzy , unmanageable and difficult to style.

More moisture inside hair fiber breaks the hydrogen bond of keratin protein and thus under high humidity conditions, hair becomes weaker and fragile.

Damaged hair fibers are more susceptible to this problem and are known to suffer severely. This is due to their higher porosity with more space for water molecules to fill in.

At low humidity conditions, hair loses water molecules as the surrounding air is drier and contains less amount of water. Here again, hair becomes rigid and dry. It loses its natural volume, body, and sheen.

Curly hair has unique structure features all along its shaft. The curl pattern exhibits some fragile points along the shaft where the hair fiber is vulnerable to break when physical force is applied.

Repeated chemical processing, combing, brushing, and environmental insults may make curly hair even weaker and exposed to weather changes.


Humectants are molecules having a greater tendency to attract and hold water molecules. Applying these molecules to the scalp or hair shaft can impart moisture to the fiber.

They work intelligently to influence (or disturb) the two-way traffic of water molecules across the hair shaft (in and out).

Humectants have several advantages and disadvantages for curly hair, and their effectiveness is often contingent on the amount of moisture in the air.

In a wet and humid environment, dry hair rapidly absorbs moisture (water) from the air. If not controlled (or hair is not protected), this could lead to hair becoming swelled and frizzy.

If you live in an area with high humidity, you have probably noticed how your hair swells up on humid days. This is because the extra moisture in the air is being absorbed by your hair, causing it to swell and become frizzy.

Glycerin is a type of humectant that is often used in hair care products, and humectants are not all created equal. The ways in which different humectants react in the hair varies.

Humectants applied to the hair draw water to themselves from whichever source is greater — the atmosphere or the hair.

Humectants are a very broad category that includes:

  • glycerine
  • salts
  • plant gels, such as aloe vera
  • algae extracts
  • hyaluronic acid
  • hydrolyzed proteins
  • sodium PCA
  • lactic acid
  • witch hazel (without alcohol)

Humectants come in a variety of subgroups. The main contender and majority of issues that people have with humectants are with the polyhydric alcohols.

  • glycerine
  • propylene glycol
  • butylene glycol
  • sorbitol
  • honey (sometimes)
  • agave nectar
  • panthenol

Their water holding capacity varies depending upon their molecular structure. Aloe vera and polymers are also known for the same reasons.

Humectants: high humidity vs. low humidity

Humectants work two ways and that is that they attract water molecules from the environment (external) as well as moisture already present inside the hair shaft (internal).

They extract moisture from where ever it is available and their function is greatly influenced by the dew point and humidity.

At high humidity levels, we got more moisture in the air and less in the hair, while humectants work to attract water molecules from the air and deliver it to hair.

However, the opposite may also happen, at low humidity and dry conditions (low water in the air), they can extract water from the scalp, skin, or hair shaft.


Anti-humectants are used to prevent the moisture in the environment from being absorbed by the hair.

They work as a barrier on the hair shaft and scalp, not allowing water molecules to enter.

Some of these ingredients are:

  • lanolin
  • waxes
  • oils (coconut, olive, castor)
  • silicones
  • pomades
  • shea butter
  • mango butter, etc.

These ingredients help keep moisture locked in your hair and can be very helpful when the dew point is 60F (16C) and up.

They can also be combined with other products to help lock in moisture. For example, you could use an anti-humectant product with a leave-in conditioner or cream to help add moisture to your hair routine.

In summary, curly hair is more susceptible to weather changes because it is already dry and fragile and needs extra care to stay hydrated.

Applying humectants or anti-humectants can help keep curly hair healthy and hydrated depending on the level of humidity.

Applying humectants or anti-humectants can help combat against frizz caused by weather.

A Balanced Formula Matters

A glycerin-containing product that solely uses glycerin as a humectant with no emollients can be a problem. A well balanced product will avoid this pitfall.

So, always look for a balanced formulation that has both humectants as well as emollients.

There are different humectants that have diverse functions. A blend of varying sizes and molecular weights might be acceptable for someone who dislikes glycerin-only products or those with no emollients or film formers.

Natural oils and butter are key players because their coating over the hair shaft can preserve the hair fiber against the weather changes and outside humidity and dew point.

During winter, avoid products having high humectant levels as it will help combat dry frosty conditions.

Also, on rainy days, the rain increases the moisture content in the air and thus has a strong impact on hair, so it’s best to avoid products with high humectant levels.

Other Considerations

There are individuals who live in dry climates that can use glycerin with no issues. Then, there are those who can only use glycerin when the humidity/dew point is “just right”.

It really varies from person to person. You have to experiment with different products and dew points to see what works best for you.

There is no one-size-fits-all solution to determining how your hair will react because it isn’t simply a porosity issue. There are three broad types of porosity by the way; low, medium, and high.

It’s all about the weather and climate, the products you use in your hair, how sensitive your hair is to increased friction, and how frequently you go outside, etc.

Unfortunately, there’s no easy rule to follow. It’s all about trial and error. (I know, it’s so frustrating.)

So, for a very quick summary. When the air is not dry, humectants like glycerin, propylene, and sorbitol are small molecules that hold water. But when the air is dry, they have the ability to pull water from your hair.

Much of how strongly an ingredient can pull water from your hair has to do with how much is present in the formula, how strongly it attracts water to itself, and whether or not the formula includes ingredients which slow water loss, such as oils or conditioners.

It is possible that humectants such as glycerin, propylene glycol, and sorbitol could pull water from your hair when the indoor/outdoor humidity/dew point drops.

This may result in a dry tacky feel, frizz, and having a “flash dry” effect. Some of this is caused by the product’s interaction with the dry air.

But, it could also be due to the product (containing glycerin) itself drying out your hair.

Some individuals can work around this issue by using a leave-in conditioner, curl cream, or oil underneath their glycerin-containing product to help protect their hair.

The Glycerin Debate: During Winter

Glycerin is often a hotly debated topic, particularly in the curly hair community.

There are those who feel that it’s a “holy grail” product, while others believe that it’s nothing more than a cheap way to add moisture to a product.

There are also those who feel that it’s a necessary evil, while others believe that it’s something to be avoided at all costs.

So, what’s the deal?

Some people believe that because the air does not have enough moisture, it dries out the hair during the winter. Therefore, they feel that products containing glycerin are more likely to cause dryness and frizz.

When you use a product with glycerin in it, since steam is humid air, it will act to help glycerin attach water without necessarily wetting your hair.

If you live in a dry climate, glycerin will take moisture from your hair and transfer it into the air instead of taking moisture from the air and transferring it to your hair to prevent your hair from becoming dry and brittle.

Tips for how to use glycerin in a dry climate:

🔷  Take a warm shower while wearing a shower cap, then take it off for the last couple of minutes before getting out of the shower. The moisture from the steam will bind to the glycerin and make your hair strands super moisturized.

🔷  You can also use a handheld steamer for a couple of minutes, but keep it at a distance and lightly steam your hair, then finish by adding a tiny amount of sealing oil. This will help to act as a barrier to keep water on the surface of your hair from evaporating.

🔷  Covering your hair with a hat, hood, or scarf while out in the cold not only helps you stay toasty warm, but also helps your hair retain moisture by providing a physical barrier against the elements.


Seasons change and so will your hair needs. Just like you change your wardrobe with the seasons, you should also switch up your hair products. By having a few key products on rotation, you can make sure your hair always looks its best, no matter the weather.

Understanding the dew point, humectants, and humidity will help you pick the right products for your hair and the current weather conditions. So don’t be afraid to experiment with different products until you find ones that work best for you and your hair type.

And remember, what works in the winter may not work in the summer (and vice versa). So be sure to have a few different options on hand, depending on the season.

Thanks for reading. until next time! 

Your turn! What seasonal changes do you notice in your hair? Let me know in the comments below!

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