逆者，四肢逆而不温也，厥者，冷也，又甚于逆。四肢者，诸阳之本，常宜和
暖，如指头微寒者，阳气衰也（阳气起于十指之端），足心冷者，阴气胜也（阴脉集于足下而趣于足心）。
如疮本焦黑，烦渴顿闷，喘促而厥逆者，此阳毒内陷，热气逆伏，手足为之冷，所谓热深厥亦深，火极似水者。
如疮本灰白，泄利而厥逆者，此元气虚惫，阴阳不相顺接，而手足为之冷也。疮疹之候，头常欲凉，足常欲温，故
头温足冷者不治。厥逆乃疮家恶证也。
如因热深而厥者，大便不通，三乙承气汤（便闷）主之。疮黑者，百祥丸、牛李膏主之（俱见黑陷）。如因泄
利气虚而厥者，陈氏木香散（泻）、异功散（出不快）主之。但十指头微寒者，四君子汤（不能食）理中汤（吐利）并加
桂主之。痘疮发热，手足却宜和暖，虽云足属肾，要凉，凉非冷也，只与常人同，遍身皆热，而此同常人，故称
凉，亦和暖之意，非真冷也。若手足冷，由其人曾多吐泻，脾脏虚怯，脾主四肢，所以冷，冷为恶候，不可单用发
表，反损脾胃，宜和中、发表兼用。痘出以脾胃为主，又宜急与术作汤以饮之，不可因循空谈废事也，先以黄 建
中汤（腹痛）加防风、羌活，或四君子汤加黄 、桂枝、防风以发之，发后以四君子汤加黄 、白芍药、当归、桂
心以补脾胃，养气血，而助痘疮之成就也。
如疮始出，手足便冷者，其人先有吐利，四肢者皆禀气于胃，脾胃气弱，不得
至经，理中汤加桂主之。
参附汤 治痘疹阳气虚寒，切牙寒战，手足并冷，或吐泻不食，饮沸汤不知热，用独参汤加好真附，
炮如法者，每剂先加一钱，未应多加之，更不应，加至四五钱，或等分亦无妨，但用之以运其阳气，如已脱者，不治。
二神散 治伤冷体寒，肢冷腹痛，口气冷，难发难壮，暂用。
丁香（九粒） 干姜（一钱，煨）
上为末。每服五分，白汤送下。盖被片时，令脾胃温暖，阴反阳回，则痘变顺矣，量儿大小轻重用之。
逆，是指四肢逆冷而不温暖；厥，是指寒冷，比“逆”的程度更重。四肢是诸阳经的根本，应当保持和暖。如果手指尖微微发凉，说明阳气衰弱（阳气起始于十个脚趾的末端）；脚心发冷，说明阴气偏盛（阴脉汇聚于足下并趋向于足心）。
如果疮疹原本颜色焦黑，出现烦躁口渴、突然昏闷、气喘急促且四肢逆冷的症状，这是阳毒内陷，热气郁伏，导致手足变冷，也就是所谓的“热深厥亦深”，即火极似水的表现。
如果疮疹原本颜色灰白，伴有腹泻痢疾且四肢逆冷，这是元气虚弱疲惫，阴阳之气不能顺接，从而导致手足变冷。疮疹的证候中，头部通常希望凉爽，足部通常希望温暖，所以如果头温而足冷，属于不治之症。厥逆是疮疹患者中的危重证候。
如果是因热邪深重导致的厥逆，伴有大便不通，用三乙承气汤主治（适用于大便闷结的情况）。如果疮色黑，用百祥丸或牛李膏主治（均见黑陷证）。如果是因腹泻痢疾、气虚导致的厥逆，用陈氏木香散（适用于泄泻）或异功散（适用于痘出不畅）主治。如果只是十个指尖微微发凉，用四君子汤（适用于食欲不振）或理中汤（适用于呕吐泄泻）并加入桂枝主治。
痘疮发热时，手足应当保持和暖。虽然常说足部属肾，应当凉爽，但这里的“凉”并非指“冷”，而是与常人相同，全身都热，唯独此处与常人无异，所以称为“凉”，这也是和暖的意思，并不是真正的寒冷。如果出现手足冰冷，是因为患者之前有过多次吐泻，导致脾脏虚弱怯弱。脾主四肢，所以会出现寒冷。寒冷属于恶候，不可单独使用发表药物，否则会反而损伤脾胃。应当采用和中与发表兼用的方法。痘疮的治疗以脾胃为主，又应当紧急给予术药煎汤饮用，不可因循守旧、空谈误事。先使用黄建中汤（适用于腹痛）加入防风、羌活，或者四君子汤加入黄芪、桂枝、防风来发散；发散之后，再用四君子汤加入黄芪、白芍药、当归、桂心来补益脾胃，滋养气血，从而帮助痘疮成熟痊愈。
如果疮疹刚发出，手足就变冷，说明患者先前已有吐利症状。四肢的气血皆禀受于胃气，若脾胃气弱，气血无法到达经脉，用理中汤加入桂枝主治。
参附汤：治疗痘疹阳气虚寒，出现咬牙寒战、手足俱冷，或呕吐泄泻、不能进食，喝热水也不知道烫手。用法是用独参汤加入优质的真附子，炮制符合规范者，每剂先加一钱，如果没有见效则多加剂量，如果仍不见效，可加至四五钱，或者人参附子等分使用也无妨。目的是运化其阳气，如果阳气已经脱失，则无法救治。
二神散：治疗感受寒邪、体质虚寒，出现肢体寒冷、腹痛、口气冷、痘疹难以发出也难以壮实的情况，暂时使用。
药材：丁香（九粒）、干姜（一钱，煨制）。
将上述药材研为细末。每次服用五分，用温水送服。盖上被子片刻，使脾胃温暖，阴退阳回，则痘疹变为顺证。根据患儿的大小轻重调整用量。
Ni (Reversal) refers to the limbs being cold and not warm; Jue (Coldness) refers to extreme cold, which is more severe than Ni. The limbs are the root of all Yang meridians and should normally be warm and comfortable. If the fingertips are slightly cold, it indicates a deficiency of Yang Qi (Yang Qi originates from the tips of the ten toes); if the soles of the feet are cold, it indicates an excess of Yin Qi (Yin meridians converge at the soles of the feet and tend toward the sole center).
If the sores were originally scorched black, accompanied by irritability, thirst, sudden drowsiness, rapid breathing, and limb reversal/coldness, this is due to Yang toxin sinking inward, with heat qi stagnating and suppressing, causing the hands and feet to become cold. This is what is called "the deeper the heat, the deeper the Jue," or fire reaching its extreme resembling water.
If the sores were originally grayish-white, accompanied by diarrhea and dysentery and limb reversal/coldness, this is due to the exhaustion of Yuan Qi (Original Qi), where Yin and Yang Qi fail to connect smoothly, causing the hands and feet to become cold. In the manifestations of sores/rashes, the head usually desires coolness, while the feet usually desire warmth. Therefore, if the head is warm but the feet are cold, it is considered incurable. Limb reversal/coldness is a malignant syndrome in patients with sores.
If the Jue is caused by deep-seated heat, accompanied by constipation, San Yi Cheng Qi Tang (Three-Yi Purgative Decoction) is the primary prescription (indicated for abdominal fullness and constipation). If the sores are black, Bai Xiang Wan (Hundred-Auspicious Pills) or Niu Li Gao (Ox Plum Paste) are indicated (both seen in Black Sunken Syndrome). If the Jue is caused by diarrhea/dysentery and Qi deficiency, Chen Shi Mu Xiang San (Chen's Costus Powder) (indicated for diarrhea) or Yi Gong San (Benefit the Work Powder) (indicated for poor eruption) are indicated. If only the ten fingertips are slightly cold, Si Jun Zi Tang (Four Gentlemen Decoction) (indicated for inability to eat) or Li Zhong Tang (Regulate the Middle Decoction) (indicated for vomiting and diarrhea) combined with Gui Zhi (Cinnamon Twig) are indicated.
When fever occurs with smallpox, the hands and feet should remain warm and comfortable. Although it is often said that the feet belong to the Kidney and should be cool, here "cool" does not mean "cold." It means they are the same as those of a healthy person: the whole body is hot, but the feet are no different from normal, hence termed "cool." This also implies warmth and comfort, not true coldness. If the hands and feet are cold, it is because the patient previously suffered from frequent vomiting and diarrhea, leading to Spleen deficiency and weakness. Since the Spleen governs the four limbs, coldness results. Coldness is a malignant sign; one must not use exterior-releasing methods alone, as this would further damage the Spleen and Stomach. One should combine methods to harmonize the middle and release the exterior. The treatment of smallpox focuses on the Spleen and Stomach; therefore, one should urgently administer decoctions containing Atractylodes Macrocephala Rhizome (Baizhu) for drinking, avoiding procrastination and empty talk. First, use Huang Jian Zhong Tang (Yellow Regulate the Middle Decoction) (indicated for abdominal pain) added with Fang Feng (Saposhnikovia Root) and Qiang Huo (Notopterygium Rhizome), or Si Jun Zi Tang (Four Gentlemen Decoction) added with Huang Qi (Astragalus Root), Gui Zhi (Cinnamon Twig), and Fang Feng (Saposhnikovia Root) to release the exterior. After releasing the exterior, use Si Jun Zi Tang (Four Gentlemen Decoction) added with Huang Qi (Astragalus Root), Bai Shao Yao (White Peony Root), Dang Gui (Angelica Sinensis Root), and Gui Xin (Cinnamon Heart) to tonify the Spleen and Stomach, nourish Qi and Blood, and assist in the maturation of the smallpox lesions.
If the sores have just erupted and the hands and feet are already cold, it indicates the patient previously had vomiting and diarrhea. The Qi and Blood of the four limbs are derived from Stomach Qi; if Spleen and Stomach Qi are weak, it cannot reach the meridians. Li Zhong Tang (Regulate the Middle Decoction) added with Gui Zhi (Cinnamon Twig) is indicated.
Shen Fu Tang (Ginseng and Aconite Decoction): Treats Yang Qi deficiency and coldness in smallpox/rashes, characterized by teeth chattering, shivering, cold hands and feet, or vomiting/diarrhea with anorexia, and drinking boiling water without feeling heat. Use Du Shen Tang (Single Ginseng Decoction) added with high-quality genuine Fu Zi (Aconite Lateral Root), prepared according to standard methods. Start each dose with 1 qian; if there is no response, increase the dosage. If still ineffective, increase to 4-5 qian, or use equal parts, which is also acceptable. The purpose is to circulate Yang Qi. If Yang Qi has already collapsed, it is incurable.
Er Shen San (Two Deities Powder): Temporarily used for injury by cold and constitutional coldness, presenting with cold limbs, abdominal pain, cold breath, and difficulty in eruption and strengthening of the rash.
Ingredients: Ding Xiang (Caryophylli Flos) (9 grains), Gan Jiang (Zingiberis Rhizoma Recens/Prepared) (1 qian, roasted).
Grind the above into powder. Take 0.5 fen per dose, washed down with warm water. Cover with a blanket for a period of time to warm the Spleen and Stomach, causing Yin to retreat and Yang to return, thus transforming the smallpox into a favorable course. Adjust the dose according to the child's age and severity.