Hair is one of the most complex & versatile structures in nature. It is composed largely of keratin, a protein that also forms our nails and skin. Keratin is arranged in a complex fractal array of filaments called microfibrils, which are further organized into macrofibrils and then into fibres which give hair its strength and flexibility.

The structure of hair can, however be impacted via  various factors, such as chemical treatments, heat styling, environmental exposure, mechanical stress, and even genetic predisposition which result in reduced hair strength, elasticity, shine, and moisture, as well as increased hair breakage, split ends, frizz, and tangling. Hair damage can also affect the psychological well-being and self-esteem of individuals who suffer from it.

The main causes of hair damage can be classified into two categories: intrinsic and extrinsic. Intrinsic causes are related to the internal structure and composition of the hair, such as the keratin, melanin, and lipids that form the hair shaft and the cuticle. Extrinsic causes are related to the external factors that affect the hair, such as the chemical, thermal, and mechanical agents that alter the hair structure and integrity. Some of the most common extrinsic causes of hair damage are:

• Bleaching, dyeing, perming, and relaxing: These chemical processes can weaken the hair bonds, disrupt the cuticle layer, and reduce the hair moisture content, leading to dry, brittle, and porous hair.
• Blow-drying, curling, straightening, and brushing: These thermal and mechanical processes can generate high temperatures and friction that can damage the hair cuticle and cortex, resulting in hair breakage, split ends, and loss of shine.
• Ultraviolet radiation, pollution, and chlorine: These environmental factors can oxidize the hair pigments, proteins, and lipids, causing hair colour fading, protein degradation, and lipid depletion, resulting in dull, weak, and dry hair.

The effects of hair damage can be observed at different levels of the hair structure, from the cuticle to the cortex. Some of the most common effects of hair damage are:

• Cuticle damage: The cuticle is the outermost layer of the hair that protects the inner layers from external damage. Cuticle damage can manifest as lifted, cracked, or missing cuticle scales, which expose the cortex and make the hair more vulnerable to further damage. Cuticle damage can also affect the hair appearance, making it rough, dull, & prone to frizz / tangling.
• Cortex damage: The cortex is the middle layer of the hair that provides the hair strength, elasticity, and colour. Cortex damage can occur when the hair bonds are broken, the hair proteins are degraded, or the hair pigments are oxidized. Cortex damage can result in reduced hair strength, elasticity, and colour, as well as increased hair porosity and water absorption.
• Lipid damage: The lipids are the fatty substances that coat the hair surface and fill the spaces between the cuticle scales. Lipid damage can occur when the lipids are depleted or oxidized by chemical, thermal, or environmental factors. Lipid damage can affect the hair moisture, shine, and smoothness, as well as increase the hair static and friction.

Consumers are becoming increasingly sophisticated in their hair needs and are looking for products that counteract the damage to  hair, nourishing, protecting, and repairing hair in addition to enhancing appearance. This presentation will cover Unilever’s approach to the measurement and alleviation of damage at the level of both the cuticle and the cortex, how we deploy technology to repair damaged proteins, to replace lost surface oils and protect colour, and how the technology is validated with consumers.