Allergic dermatitis can lead to redness, itching, and swelling in the affected area It is necessary to find out which allergen is causing the reaction and avoid it. I suggest you to see a dermatologist for proper diagnosis and treatment.
 

Chicken skin is a condition whe­re your skin feels bumpy, and rough, like­ sandpaper. Keratin buildup blocks hair follicles, causing this. Using mild cle­ansers helps. Moisturize ofte­n. Gentle exfoliation smooths bumps. Lactic acid or ure­a products reduce roughness. It's common but usually improve­s gradually. 

There are many treatments for acne dark spots like chemical peels, laser treatments, certain ointments etc. But I suggest you to first visit a dermatologist in person. Based on your individual condition, the doctor will be able to recommend the best treatment for you. 

It seems your neck is a bit swollen but you are not feeling any pain. This could be caused by an infection or a swollen gland. Sometimes, it can occur without any serious reasons as well. However, the priority is to have a doctor take a look at it to be on the safe side. They may have to conduct some tests to be able to tell what is going on. 

It is possible that the black vertical line on the boy's thumb nail is a result of a melanonychia striata, which is a linear nail melanin pigmentation. It is relatively common in children and is generally harmless. However, it is important to have it evaluated by a doctor, especially if it is growing, to rule out any underlying medical conditions.

It seems that dandruff might be one of the conditions. The main symptom of dandruff is itching, and white particles of skin can be seen on hair. Sometimes, this condition might also produce red patches on the face, especially around the hairline area. The pathogen fungi on your scalp cause dandruff. For example, choose a shampoo that is specifically designed for dandruff. In particular, washing hair regularly along with the stress management procedure may also be beneficial for you.