Some keratin products to straighten hair contain formaldehyde, and the use of this substance is associated with several symptoms, including rashes, watery eyes, and headaches. Report it through the Internet, and read the safety data of the materials used in its manufacture. 
Damage to hair
Hormonal changes in the normal situation lead to the loss of a small amount of hair at a rate ranging between fifty to one hundred, but the chemicals lead to the loss of large amounts of hair, which makes it weaker and thinner, and hair loss affects the roots of the hair negatively, and pushes the hair to separate About it,  and repeated treatments cause dry hair , and increase susceptibility to external factors, such as: the environment, the sun, heat styling tools, and hair products, so it is important to take sufficient time to treat the hair before repeated straightening processes. 
Damage to the scalp
Excessive use of chemicals increases the chance of hair loss , which makes the scalp more prone to cracking, and causes itching, which is one of the causes of dandruff,  and chemical burns can cause skin breakdown and dissolution, which is very painful, and can also cause infections. Secondary, permanent hair loss, and the degree of these burns ranges from first to third degree. 
Tips to avoid damage from straightening hair
Some things must be taken into consideration to enjoy smooth hair away from the potential damage caused by chemical straightening, including: 
- Proper care of hair after treatment; In order to avoid hair dryness, brittleness and falling out.
- Ensure that the professional hair straightener maintains a distance between chemicals and the scalp; This is to avoid itching, redness, and a rash.
- Not to repeat straightening hair before the passage of a year.
- ↑ Shelley Levitt, “What You Need to Know About Hair-Smoothing Treatments” , www.webmd.com , Retrieved 28-10-2017. Edited.
- ^ A b 18-9-2017 (Shruti Goenka), "7 Side Effects Of Hair Smoothing You Should Be Of - Aware" , Www.stylecraze.com , Retrieved 28-10-2017. Edited.
- ^ A b KATHY MAYSE (18-7-2017), "What 'Post Are The Dangers Of Hair Reviews Relaxing?" , Www.livestrong.com , Retrieved 18-10-2017. Edited.
- ↑ Bhakti Paun Sharma (26-8-2015), “Think about these side effects before you choose hair straightening” , www.thehealthsite.com , Retrieved 28-10-2017. Edited.