Here are a few options for a WordPress post_tag description, targeting slightly different aspects of the topic, all in Traditional Chinese:

**Option 1 (Most straightforward):**

* **Title:** 免疫力下降
* **Description:** 了解免疫力下降的成因、症狀，以及如何提升免疫力、應對健康挑戰。 (Learn about the causes and symptoms of weakened immunity, and how to boost your immune system to overcome health challenges.)

**Option 2 (Focus on Symptoms):**

* **Title:** 免疫力下降
* **Description:** 常感疲勞、容易感冒？探討免疫力下降的相關症狀，以及如何透過飲食、運動等改善身體狀況。 (Are you often tired or prone to colds? Explore the symptoms associated with weakened immunity and how to improve your health through diet, exercise, etc.)

**Option 3 (More preventative/holistic approach):**

* **Title:** 免疫力下降
* **Description:** 守護健康！ 了解免疫力下降對身體的影響，學習打造強健免疫系統的秘訣，包括生活習慣、飲食調整等等。 (Protect your health! Learn about the impact of weakened immunity on the body and discover the secrets to building a strong immune system, covering lifestyle habits, dietary adjustments, and more.)

**Option 4 (Short and concise):**

* **Title:** 免疫力下降
* **Description:** 免疫力下降的相關資訊，包括原因、徵狀及改善方法。 (Information about weakened immunity, including causes, symptoms, and how to improve it.)

**Important Considerations:**

* **Target Audience:** Consider who your target audience is (e.g., general public, health-conscious individuals, etc.) when choosing the best description.
* **SEO:** Think about keywords. You might consider adding related terms. (e.g., “感冒” – cold, “抵抗力” – Resistance, “健康” – Health). You can subtly include them without making the description clunky.
* **Post Content:** The description should accurately reflect the kind of content you’ll be posting under this tag.

**How to use these in WordPress:**

1. Go to **Posts > Tags** in your WordPress dashboard.
2. Either create a new tag or edit your existing “免疫力下降” tag.
3. In the “Description” field, paste the chosen description.
4. Click “Update” or “Add New Tag”.

Choose the description that best suits your content and goals! Good luck!