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What Happens if You Leave Hair Dye on Too Long?

What Happens if You Leave Hair Dye on Too Long - a girl getting her hair dyed at a salon
a girl getting her hair dyed at a salon

Hair dyeing is common these days almost among all age groups for enhancing beauty, as it gives a different stylish look to your personality. We all think about several things regarding hair dyeing, like which color suits us.

Despite this, another thing needs consideration for our hair health, such as if hair dye remains in your hair for long, what will happen is an important question. Let’s move ahead to get the answer to this question:

Types of Hair Dye

hair dyes of different colors
hair dyes of different colors

Hair dyes are essential in today’s fashion. People have been using hair dyes for many years. We should know about dyes and their types in detail before proceeding with their effects on the hair. There are two types of hair dyes:

Semi-Permanent or Non-Permanent Dye

The adverse effects of this dye on staying long on hair are limited and less penetrating due to a lack of ammonia and peroxide. These two compounds are responsible for deep penetration by removing the natural pigmentation of hair strands.

Permanent Hair Dye

This dye produces strong effects by bringing a change in the molecular composition of the hair cortex. As it moves deeper inside the hair cuticle, it does not fade away quickly.

Why Should Hair Dye not Stay on Hair for a Long Time?

a girl getting her hair dyed from a hairdresser
a girl getting her hair dyed by a hairdresser

There are many harmful compounds present in hair dye that do not allow prolonged stay. You can read our article “How Long to Wait to Wash Hair After Coloring?” for more information!

Some fake manufacturers prepare hair dyes that harm your hair on use. So you must know all the harmful compounds in hair dye to avoid excessive exposure.


Ammonia is the most common compound in hair dye. According to NCBI, permanent hair dyes often have ammonia to open hair cuticles. So, it penetrates deep inside your hair cuticle.

Being highly penetrating and ideal for dye, its excessive amount for a long time causes dryness and damage. In some cases, it causes throat irritation and respiratory problems.

Para-Phenylenediamine (PPD)

This compound is present in both dyes, permanent and semi-permanent. Although it is highly effective, it has severe side effects, such as allergies on the scalp.

The allergic reaction caused by this compound makes your scalp skin highly sensitive, and its long-term contact causes heart and respiratory issues.

According to NHS, your face and scalp can be itchy and begin to swell if you are allergic to PPD. Your entire body could experience symptoms, e.g., itchiness and discomfort.

Titanium Dioxide

It Is one of the most common ingredients but highly carcinogenic, so most experts recommend avoiding its use to reduce the effects of cancer.

According to research, exposure to titanium dioxide can irritate the eyes, nose, throat, and lungs. Repeated exposure can result in bronchitis, which manifests as coughing up mucus and having trouble breathing.


People with susceptible skin should avoid this compound, which causes a severe allergic reaction. If you inhale this combustible compound by mistake, you will suffer abdominal problems.

According to Safe Cosmetics, resorcinol is toxic in larger doses and can disturb central nervous system performance. It can cause respiratory issues. It can interfere with thyroid function and the endocrine system.

Leaving Dye on Hair for Longer Duration Results In?

a girl dyeing her hair
a girl dyeing her hair

The recommended time for leaving the dye on hair is 30-40 minutes. If it stays more, outcomes depend on different factors such as your hair structure and type of dyes. We will discuss the results in detail on both aspects.

Permanent Hair Dye

If you leave the permanent hair dye for a long time, it will damage your hair drastically with its strong chemicals. The dye will give a darker color tone to your hair and move away rapidly. The hair will become weak and broken upon tangling, and you will also face split ends. The hair will be deprived of moisture and nutrients.

Non-Permanent Hair Dye

This does not affect severely if left for long. The reason is that it is less penetrating and has the least reactive chemical. But still, it is advisable that it also shouldn’t remain on your hair for a long time as it makes your hair dull and rough.

Hair Structure

There are three types of hair thickness:

  • Thin
  • Thick
  • Medium

The thin hair strands take less, about thirty minutes, to adopt color compared to medium thickness. Similarly, medium thickness takes more time than thin but less than thick.

So it is understood that dye that remains on thin hair for a long time damages your hair more than thick or medium hair. Thin hair takes 30 minutes for proper dying without damage, medium hair requires 40 minutes, and thick hair takes more time.

Hair Texture

If your hair is porous, it can absorb moisture quickly and takes less time to dye. The porosity varies from high to low. It can be determined by dipping your hair in the water.

Highly porous hair sinks in water in less than 5 minutes, and less porous will float on water. It shows if your hair is highly absorbent and dye remains on it for a long time, it will affect your hair in terms of dryness and darker color tone.


You have countless styling options for your hair, including highlights, hair dyes, and other things! Although all the instructions are written on hair dyes on how to use them and how long they should stay on hair.

The timing results of hair dye vary from person to person. Removing dye after 30 to 40 minutes is preferable, so your hair doesn’t become frizzy, dull, or brittle, develop a darker shade, and have split ends. You should take care of your hair and don’t let the dye stay more than the given time.


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