Can the Nexplanon (etonogestrel) implant cause hives (urticaria)?

Can Nexplanon Cause Hives?

Yes, Nexplanon can cause hives (urticaria), though this is a rare adverse reaction. The FDA drug label explicitly lists urticaria among the skin and subcutaneous tissue disorders reported during post-approval use of both Implanon and Nexplanon 1.

Evidence from FDA Drug Labeling

The official Nexplanon prescribing information documents urticaria as a recognized adverse reaction identified during postmarketing surveillance 1. While the exact frequency cannot be reliably estimated from spontaneous reporting systems, the FDA label also notes other hypersensitivity reactions including:

• Angioedema (including aggravation of pre-existing angioedema or hereditary angioedema)
• Anaphylactic reactions
• Other skin reactions (pruritus, rash, seborrhea)

Patients with a known allergy to anything in Nexplanon should not use this contraceptive method 1.

Mechanisms and Clinical Context

The development of hives with Nexplanon can occur through several pathways:

Progestogen Hypersensitivity

Documented case reports describe delayed-type hypersensitivity reactions to etonogestrel implants 2, 3. One case presented with marked eosinophilia that resolved after implant removal 2, while another showed delayed-type hypersensitivity that similarly resolved upon removal 3. These represent rare but genuine immunologic reactions to the progestogen component.

Local Reactions vs. Systemic Urticaria

It's important to distinguish between:

• Local insertion site reactions (more common): pain, itching, bruising, dermatological changes at the implant site 1
• Systemic urticaria (rare): generalized hives that may indicate true hypersensitivity

Barium Sulfate Reactions

Nexplanon contains 15 mg of barium sulfate for radiographic visibility. While extremely rare, allergic reactions to this component have been documented, with at least one case report of a local reaction that resolved only after implant removal 4.

Clinical Management Algorithm

If a patient develops hives after Nexplanon insertion:

1. Assess timing and distribution

   • Immediate onset (within hours): consider anaphylactic/IgE-mediated reaction
   • Delayed onset (days to weeks): consider delayed-type hypersensitivity
   • Localized to insertion site: may be local reaction rather than systemic urticaria
   • Generalized distribution: suggests systemic hypersensitivity

2. Evaluate for other causes

   • New medications or supplements
   • Dietary changes
   • Concurrent infections
   • Pre-existing chronic spontaneous urticaria (which affects ~20% of women at some point and may be exacerbated by hormonal changes) 5, 6

3. Initial treatment approach

   • For mild urticaria: trial of non-sedating H1 antihistamines (e.g., cetirizine, loratadine) at standard or increased doses 7
   • For severe or persistent urticaria: consider adding H2 antihistamines 7
   • Document response to treatment

4. Definitive management

   • If urticaria persists despite antihistamine therapy or recurs when antihistamines are discontinued, removal of the implant should be strongly considered 2, 3
   • Case reports consistently show resolution of symptoms after implant removal
   • Offer alternative non-hormonal contraception or a different hormonal method

Important Caveats

• The French pharmacovigilance data from 10 years of surveillance (5,433 adverse events) reported 524 skin reactions among all adverse events, though specific breakdown of urticaria cases was not provided 8
• Most adverse reactions to Nexplanon are not serious, but hypersensitivity reactions warrant attention 8
• Patients should be counseled that if they develop generalized hives, difficulty breathing, or signs of anaphylaxis, they should seek immediate medical attention
• Consider pre-existing chronic urticaria as a relative consideration before insertion, as hormonal fluctuations may exacerbate the condition 5

The key clinical pearl: while bleeding irregularities are the most common reason for Nexplanon discontinuation, true hypersensitivity reactions including urticaria do occur and typically require implant removal for resolution.