Blisters and Erosions in Pemphigus and Pemphigoid

What the blister is actually telling you

By the time you read this you have probably been told it is an allergy, been given an antihistamine, and watched it do nothing. It is not an allergy. In pemphigus and pemphigoid the blister is a structural failure: your immune system has made antibodies against the proteins that hold your skin together, and the skin has come apart at a specific level. Which level it comes apart at is most of the diagnosis — and it is why two diseases that both make blisters behave so differently.

Pemphigus: the split is inside the epidermis

Skin cells are riveted to each other by desmosomes. Two of those rivet proteins — desmoglein 1 and desmoglein 3 — are the targets in pemphigus. When antibodies bind them, the cells come unstuck from one another (acantholysis) and the skin splits within the epidermis. The roof of the blister is therefore only a few cell layers thick.

What that produces:

• Flaccid blisters. Soft, wrinkled, sagging under their own fluid rather than doming up.
• They rupture almost immediately. Many people never see an intact blister at all. They see raw, weeping erosions and crusts, and cannot understand why the doctor keeps calling it a blistering disease.
• Nikolsky sign positive. Firm sideways pressure on skin that looks entirely normal shears the top layer away. Your dermatologist may test this.
• Pemphigus vulgaris (mainly anti-desmoglein 3) usually involves the mouth — and very often the mouth comes first, sometimes months before any skin lesion.
• Pemphigus foliaceus (anti-desmoglein 1) is more superficial still: scale and crust rather than obvious blisters, typically on the scalp, face, upper chest and upper back, and it spares the mouth completely.

Pemphigoid: the split is underneath the epidermis

Here the target is different. BP180 (collagen XVII) and BP230 are components of the hemidesmosomes — the anchors fastening the bottom row of epidermal cells down onto the dermis. Antibodies bind them, complement is activated, eosinophils and mast cells arrive and release proteases, and the epidermis lifts off the dermis as one intact sheet.

• Tense blisters. Domed, firm, persisting for days.
• Often large, sometimes blood-stained, frequently sitting on red or hive-like skin.
• Common on the inner thighs, lower abdomen, groin, flexures and forearms, often symmetrically.
• Usually non-scarring, though pigment change and small white cysts (milia) are common as they heal.
• The person is typically elderly, and the itch usually came first — often months before the first blister.

The erosion is the disease; the blister is only the event

A blister is transient. What persists — what hurts, weeps, becomes infected, keeps you awake and takes weeks to close — is the erosion underneath it. In pemphigus, the erosion is the whole clinical picture. When large areas are eroded the skin stops doing its job: fluid, protein and heat are lost, and bacteria get in. That is why severe pemphigus is nursed with the seriousness of a burn, and why untreated pemphigus vulgaris is a disease that kills people.

Things that look like this and are not

• Inherited epidermolysis bullosa (EB). A genetic mutation in the proteins that hold skin together, usually apparent from birth or infancy, blistering with friction. It is not autoimmune, and no treatment reverses it — ours or anyone else's. Only EB acquisita, which is autoimmune and appears in adults, belongs in the same conversation as pemphigus and pemphigoid.
• Bullous impetigo, bullous drug eruptions, Stevens-Johnson syndrome and toxic epidermal necrolysis (acute, drug-triggered, and a medical emergency), dermatitis herpetiformis (ferociously itchy grouped vesicles, linked to coeliac disease), pompholyx, contact reactions, burns, friction.

Only a biopsy settles it. Perilesional skin sent for direct immunofluorescence (DIF) is the definitive test — it shows antibody deposited in the tissue, and it separates these diseases from everything listed above. A blood ELISA then gives an antibody titre (anti-desmoglein 1 and 3, or anti-BP180) that tracks how active the disease is over time.

What to record — because it is what we will ask you for

• Count NEW blisters or erosions each week. Not the total; the new ones. Total lesion count moves slowly and demoralises you. New-lesion count is the first thing that changes when treatment starts working — and the first thing that changes when it stops.
• Photograph the same one or two lesions weekly, in the same light, so you can see whether erosions are closing.
• Note whether blisters are tense and persistent or flaccid and instantly raw. That single observation orients the entire diagnosis.
• Note mouth, throat, nose, genital and — above all — eye symptoms.
• Do not deliberately burst a blister. While the roof survives it is the best dressing you will ever have. If a large tense blister needs draining, a clinician does it with a sterile needle and leaves the roof in place.

Where our work sits

Everything we do is formulation-based: oral compounds and topicals, couriered to you, taken and applied at home. For most patients there is no procedure, no in-clinic therapy and no clinic visit. It is supportive care alongside your dermatologist — never instead of them, and never a reason to change what they have prescribed.

The order is the point. The sequence is Lowering Inflammatory Load, then Internal Healing and Gut Repair, then Functional Detox and Immune Balancing, then External Care (topicals you apply at home), then Sustaining Remission. External Care is deliberately fourth, because the surface is where this disease shows itself — it is not where it is decided, and a topical does not stop an autoantibody.

For the first four to eight weeks the work is internal and we do not expect your skin to look different. From months two to four the disease should begin to change. Stable remission is assessed from month eight onward. We do not promise a cure, and we publish no success rate.

When this stops being something to read about

Widespread raw skin, fever, spreading redness, foul-smelling wounds, inability to eat or drink, hoarseness or breathlessness, or any eye pain, redness or grittiness — that is same-day medical care, and eye symptoms mean an ophthalmologist urgently. Sudden withdrawal of steroid treatment is dangerous; only the doctor who prescribed it changes the dose.