You have washed, rinsed, and hang-dried your clothes. You wore them for the day, but then you realized how itchy your skin has suddenly become. Were you allergic to the fabric – or was it your laundry process?

This incident is not so uncommon. The likely reason is that your clothes were not as rinsed very well to a pH level of 7 – the level which the skin can tolerate.

Now, you ask: What is pH and why does it matter in the laundry process?

Let’s take a step back and understand the chemistry that occurs when you wash your clothes.

We know the many chemicals used in laundry. The common ones are detergents and fabric softeners.

During the washing process, enzymes in detergents help break down protein-based stains such as blood and food. Once they are smaller molecules, they can be easily washed away.

Furthermore, there are the surfactants, which surround dirt and oil molecules. When surfactants break dirt and oil from the fiber, we call that emulsification. Surfactants disperse the dirt in the water by attaching into them and keep them from re-depositing on the fabric by keeping them suspended.

There is also the saponification process where sodium hydroxide (an ingredient of detergents) react to the presence of fats.

Another chemical process is bleaching, which occurs to help whiten and brighten fabrics. The oxidizing work by chlorine bleach makes the color molecules in stains colorless.

Then there is the fabric softening, which helps the fiber feel smoother and softer.

As these processes occur, the pH level fluctuates. This is a measure of the acidity or alkalinity of a solution on a scale of 0 to 14 (0 being the most acidic, while 14 being the most basic.) Lemon juice and vinegar have a pH of 2, while black coffee is 5. Beyond the neutral 7 is base. Baking soda has a pH of 9.5, while bleaches can either be acidic or basic. The pH level affects the behavior and solubility of different molecules and ions – it is an important property in chemical and biological systems.

Now, back to laundry. Detergents have a pH level of between 8 and 10, which are alkaline. Alkaline solutions are more effective to break down oil and grease.

If you use hard water, though, the high level of minerals (calcium and magnesium) causes the pH level of the washing process to decrease. This makes it more difficult to break down oil and grease, and result in the formation of insoluble sales that leave a residue on fabrics. You may have felt sometimes that your fabrics are stiff and rough. To counter these, detergents may contain sodium carbonate to increase alkalinity or sodium tripolyphosphate to sequester said minerals.

So…what causes itchiness?

During the rinse process, fabric softeners (acids) lower the pH level. Rinsing neutralizes the pH level to a point when it won’t do harm with human skin. By failing to rinse properly, caustic soda – present in soaps – is retained on the surface that causes skin irritation, itchiness, and dermatitis.

One can perform a litmus test or, better yet, a Phenolpthalein test after the last rinse to see the effectiveness of the process.

Overall, itchiness on skin from one’s clothes can be caused by any of the following related laundry processes:

  1. Bad quality of water
  2. Bad sorting done before the washing process
  3. Chemicals on clothes were not removed properly during the washing process
  4. Too much fabric conditioner