An individual has spent too much time sun bathing. Not only is his skin painful to touch, but small blisters have appeared in the affected area. This indicates that he has damaged which layers of his skin

Epidermis layer of the skin will be most affected and blisters indicates that dermis layer of skin has also been affected.

Explanation:

The sunlight contain ultraviolet radiations which can damage the skin. The UV radiations causes serious damages to DNA and other parts of the cells directly and also by the production of free radicals. These radiations damage the DNA and cell tries to rectify them. These damages to DNA causes problems in cell replication through errors in DNA replication. If the damage is too frequent that cell can't repair it the immune response will destroy the cell.

Epidermis is the outermost layer of skin which protect the internal cells from external damages and dermis is present beneath the epidermis and it provides nutrient rich blood to epidermis. If the UV radiations are too intense they can penetrate more deeper and can damage the dermis also.

Skin burn can occur in less than 15 minutes depending upon the intensity of UV radiation. The skin become red and blisters appeared on skin. More chronic skin burn can also cause fever, chills and even death.

The dermis and epidermis must have been affected.

The dermis formed the outermost layer of the skin. it is made up of layers of stratified squamous epithelium cells, (group of tough flat cells) which separate and protect the skin from external environment. The cells of the upper epidermis are non-living and fragile in structure, since they lack a direct blood supply; therefore it is easier for them to form broken blisters when exposed to tension or heat as experienced in the question. The older cells are usually remove or washed away and replaced before the lower cells are exposed.

Therefore the blisters is from the epidermis. (upper). Cells of lower epidermis or subepidermis have high tenser strength are not easily broken, therefore the blisters can not be from this part.

The dermis is the living part of the skin it is made up of blood vessels, nerves (sensitive to temperature change), and sweat glands. it is separated from the epidermis by the basement membrane.

It is the inflammation of these nerves which synapse with receptors sensitive to temperature, pressure, tactile simulations, that resulted to pain experienced by the individual in the question.

Since the cells of the dermis are well innervated the sensation of pain and heat must have been received by the pain receptors in the dermis.