Cellulitis: This is a common bacterial skin infection that can cause redness, swelling, and warmth of the skin, often accompanied by boils and blisters. The localized nature of the symptoms to one arm suggests a localized infection such as cellulitis.

Abscesses: These are localized collections of pus that can occur on the skin and are often accompanied by swelling, redness, and warmth. Multiple abscesses could present similarly to boils and blisters.
Folliculitis: An inflammation of the hair follicles, which can cause small, pus-filled bumps (boils) and can be accompanied by swelling if severe.
Contact Dermatitis: An allergic or irritant reaction to something that has come into contact with the skin, which can cause blisters, swelling, and boils in severe cases.

Necrotizing Fasciitis: A severe infection that destroys the tissue under the skin, including fat and the tissue covering the muscles (fascia). It's a medical emergency and can be fatal if not treated promptly. Early signs can include swelling, redness, and pain, which might initially resemble less severe conditions.
Deep Vein Thrombosis (DVT): While DVT typically presents with swelling, warmth, and sometimes discoloration of the limb, it is crucial to consider, especially if there's a history of immobility, cancer, or other risk factors for DVT. The presence of boils and blisters would be atypical but could potentially occur if there's associated skin infection or reaction.
Sepsis: If the infection is severe and has entered the bloodstream, it could lead to sepsis, a life-threatening condition. Symptoms can include fever, chills, rapid heart rate, and in severe cases, confusion or disorientation.

Erysipelas: A type of skin infection that affects the upper layer of the skin, often caused by streptococcal bacteria. It can cause a bright red, raised rash, typically on the face or legs but can occur on the arms.
Staphylococcal Scalded Skin Syndrome (SSSS): A condition caused by staphylococcal toxins that typically affects infants and young children, causing widespread blistering and peeling of the skin. It's rare in adults but can occur, especially in those with compromised immune systems.
Cutaneous Anthrax: A rare but potentially deadly infection caused by anthrax bacteria, which can enter the body through cuts or scrapes in the skin. It initially causes a painless, ulcerative lesion that later turns into a black eschar, surrounded by swelling.